Re: The set of necessary FISONs

On 20.02.2025 15:30, Jim Burns wrote:

AXIOM I 'extensionality' means
proving each FISON is omissible  is no
proving {F} is omissible.
 

∀n ∈ ℕ: n+1 ∈ ℕ. Together with 1 ∈ ℕ this defines the set ℕ. (*)
Addition of all numbers defined by (*) to the empty set is tantamount to addition of ℕ to the empty set.
Subtraction of all numbers defined by (*) from ℕ is tantamount to subtraction of ℕ from ℕ.
Homework: Prove the same for FISONs or v. Neumann ordinals.
Regards, WM