Prove, using the Countable Principle of Choice, that every countable subset of $\displaystyle \omega_1$ has an upper bound in $\displaystyle \omega_1$.
Notation: $\displaystyle \omega_1$ denotes the first uncountable ordinal.
Prove, using the Countable Principle of Choice, that every countable subset of $\displaystyle \omega_1$ has an upper bound in $\displaystyle \omega_1$.
Notation: $\displaystyle \omega_1$ denotes the first uncountable ordinal.