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Asaf Karagila
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Consider the following statements about a given set $X$ in in $\mathsf{ZF}$:

(1) There is $x_0\in X$ such that there is a bijectionsurjective map $\varphi: X\to X\setminus\{x_0\}$$\varphi: X\setminus\{x_0\}\to X$.

(2) There is an injective map $\iota:\mathbb{N}\to X$.

It is easy to see that (2) implies (1) in $\mathsf{ZF}$, but are they equivalent?

Consider the following statements about a given set $X$ in in $\mathsf{ZF}$:

(1) There is $x_0\in X$ such that there is a bijection $\varphi: X\to X\setminus\{x_0\}$.

(2) There is an injective map $\iota:\mathbb{N}\to X$.

It is easy to see that (2) implies (1) in $\mathsf{ZF}$, but are they equivalent?

Consider the following statements about a given set $X$ in in $\mathsf{ZF}$:

(1) There is $x_0\in X$ such that there is a surjective map $\varphi: X\setminus\{x_0\}\to X$.

(2) There is an injective map $\iota:\mathbb{N}\to X$.

It is easy to see that (2) implies (1) in $\mathsf{ZF}$, but are they equivalent?

Post Undeleted by Dominic van der Zypen
Post Deleted by Dominic van der Zypen
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Notions of infinity in $\mathsf{ZF}$ without choice

Consider the following statements about a given set $X$ in in $\mathsf{ZF}$:

(1) There is $x_0\in X$ such that there is a bijection $\varphi: X\to X\setminus\{x_0\}$.

(2) There is an injective map $\iota:\mathbb{N}\to X$.

It is easy to see that (2) implies (1) in $\mathsf{ZF}$, but are they equivalent?