Sets HW #10
Maynard (Eli Maynard). pp207-208
#26
Show that all ordinals are grounded and are their own rank We show by transfinite induction that for each ordinal $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ we have $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha \in V_{\alpha+1}$, which establishes both groundedness and rank.
If $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha = \varnothing$ then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha \in \{\varnothing\} = V_1 = V_{\alpha+1}$
Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha = \beta+1$. By the inductive hypothesis we know $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \in V_{\beta+1}$. Since $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_{\beta+1}$ is transitive then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \subseteq V_{\beta+1}$. Then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha = \beta \cup \{\beta\} \subseteq V_{\beta+1}$, so $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha \in \sc P(V_{\beta+1}) = V_{\beta+1+1} = V_{\alpha+1}$.
Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ a limit ordinal. By the inductive hypothesis for $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta < \alpha$ we know $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \in V_{\beta+1}$ and by transitivity $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \subseteq V_{\beta+1}$. Since $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ is a limit ordinal then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha = \bigcup_{\beta < \alpha} \beta$. Combining these two facts we have that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha \subseteq \bigcup_{\beta < \alpha} V_{\beta+1}$. Then note % shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\begin{align*} & \bigcup_{\beta < \alpha} V_{\beta + 1} \\&= \bigcup_{\beta <\alpha} V_\beta && \alpha \t{ has no predecessor and each } V_\beta \t{ is transitive} \\&= V_\alpha &&\t{theorem (7U)} \end{align*}
#27
Show that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\bb R$ has rank $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\omega + 5$ Note that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\bb R \in \underset{\bb R \t{ is a set of}}{\sc P}(\underset{\t{reals, each a set of}}{\sc P}(\underset{\t{rationals, each a set of}}{\sc P}( \underset{\t{pairs of}}{\times}(\underset{\t{a natural}}{\bb N}, \underset{\t{and a natural}}{\bb N}) )))$and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }A \times B = \{ \{\{a\},\{a,b\}\} : a \in A, b \in B \} \in \sc P(\sc P(A \cup B))$so $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\bb R \in \sc P^5(\bb N \cup \bb N) = \sc P^5(\bb N)$so the rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\bb R$ is $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\omega + 5$
#28
Show that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_\alpha = \{ X \mid \t{rank}(X) \in \alpha\}$ (⇒) Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X \in V_\alpha$. Then by (7S) for some $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \in \alpha$ have $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X \in \sc P(V_\beta)$. Hence $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\t{rank}(X) \ineq \beta$ and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \in \alpha$ so we’re done. (⇐) Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X$ with $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\t{rank}(X) \in \alpha$. Then for some $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta$ have both $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X \in \sc P(V_\beta)$ and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\beta \in \alpha$. By (7S) this entails $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X \in V_\alpha$; done.
#30
Show that all of the following always hold
$% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\t{rank}(\{a,b\}) = \t{max}(\t{rank}(a),\t{rank}(b))^+$
% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\begin{align*} &\t{rank}(\{a,b\}) \\&= \bigcup_{e \in \{a,b\}} \t{rank}(e)^+ &&\t{(7V)} \\&= \t{rank}(a)^+ \cup \t{rank}(b)^+ \\&= (\t{rank}(a) \cup \t{rank}(b))^+ \\&= \t{max}(\t{rank}(a), \t{rank}(b))^+ \end{align*}
$% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\t{rank}(\sc P(a)) = \t{rank}(a) +1$ The rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }a$ is the least ordinal $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ for which $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }a \subseteq V_\alpha$. Elements $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }b \in \sc P(a)$ have $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }b \subseteq a \subseteq V_\alpha$, so $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }b \subseteq V_\alpha$; hence $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\sc P(a) \subseteq V_{\alpha + 1}$ so the rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\sc P(a)$ is at most $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_{\alpha + 1}$. Also, since $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\{a\} \in \sc P(a)$ and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }a \nsubseteq V_\alpha$ then the rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\sc P(a)$ is greater than $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_\alpha$. Hence it is exactly $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_{\alpha+1}$
$% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\t{rank}\left(\bigcup a\right) \ineq \t{rank}(a)$ Let $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\upsilon$ and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ respectively be the ranks of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\bigcup a$ and $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }a$, and assume for contradiction that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }a \in \upsilon$. Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B \in A \in a$. Then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B \in \bigcup a$. Also, $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }A \in a$ so by the definition of rank have $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }A \in V_\alpha$. Since $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha \in \upsilon$ then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }V_\alpha \subseteq V_\upsilon$, so also $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }A \in V_\upsilon$. Since $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B \in A \in V_\upsilon$ then by transitivity $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B \in V_\upsilon$. Thus the rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B$ is at least $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\upsilon + 1$, but by definition the rank of $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }B$ is $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\upsilon$; contradiction.
#37
Show that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ is an ordinal exactly when it is transitive and when $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }x,y \in \alpha$ are distinct then $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }x \in y \lor y \in x$ (⇒) Follows from theorem (7M) (⇐) Take $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ transitive and with $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }(\alpha, \in_\alpha)$ abiding by trichotomy. Want to show that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\alpha$ is an ordinal; since it’s transitive then by (7L) it suffices to show that $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }(\alpha, \in_\alpha)$ is a well-order. Assume otherwise. Then some nonempty subset $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }X \subseteq \alpha$ has no minimum element. Hence for every $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }x \in X$ exists $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }y \in X$ with $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\neg(x \in y)$, which means (due to trichotomy) $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }y \in x$. By the axiom of choice this $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\forall \exists$-statement entails existence of a function $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }f : X \to X$abiding by $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }f(x) \in x$ This generates either an infinite descending $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\in$-chain or an $% shorthands \newcommand{\cl}{ \mathcal{#1} } \newcommand{\sc}{ \mathscr{#1} } \newcommand{\bb}{ \mathbb{#1} } \newcommand{\fk}{ \mathfrak{#1} } \renewcommand{\bf}{ \mathbf{#1} } \renewcommand{\sf}{ \mathsf{#1} } \newcommand{\floor}{ { \lfloor {#1} \rfloor } } \newcommand{\ceil}{ { \lceil {#1} \rceil } } \newcommand{\ol}{ \overline{#1} } \newcommand{\t}{ \text{#1} } % magnitude etc \newcommand{\norm}{ { \lvert {#1} \rvert } } % cardinality \newcommand{\card}{ \t{cd} } % disjoint untion \newcommand{\dcup}{ \sqcup } % represents an anonymous parameter % eg. f(\apar) usually denotes the function x \mapsto f(x) \newcommand{\apar}{ {-} } % tuples \newcommand{\tup}{ \langle {#1} \rangle } % reverse-order composition %\newcommand{\then}{ \operatorname{\ ;\ } } \newcommand{\then}{ {\scriptsize\ \rhd\ } } \newcommand{\pre}{{ \small {#1} }} \newcommand{\injects}{ \hookrightarrow } \newcommand{\surjects}{ \twoheadrightarrow } % category names \newcommand{\cat}{{ \bf{#1} }} \newcommand{\ineq}{ \operatorname{\underline\in} }\in$-cycle, both of which violate regularity.