Axiom: Peano Axioms

Let \(N\) be a set fulfilling the following axioms:

P1: \(N\) contains the element \(0\).
P2: For each element \(n\in N\) there exists a unique element \(n^+\), the so-called successor of n¹.
P3: There is no element \(n\in N\) such that \(n^+=0\) (i.e. \(0\) is not a successor of any element of \(N\)).
P4: If two elements \(n,~m\in N\) have the same successors \(n^+=m^+\) then they are the same \(n=m\).
P5: If a subset \(A\subset N\) contains the element \(0\) and with each element \(n\) contained in it it also contains the successor \(n^+\), then \(A\) must be the set \(N\) (principle of induction).

Explanations: 1

Branches: 1
Definitions: 2 3
Explanations: 4
Parts: 5 6
Proofs: 7 8 9 10
Propositions: 11 12

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