1+1 = 2

Theorem
Define $0$ as the only element in the set $P \setminus s \left({P}\right)$, where:
 * $s \left({P}\right)$ is the image of the mapping $s$ defined in Peano structure
 * $\setminus$ denotes the set difference.

The theorem to be proven is:
 * $1 + 1 = 2$

where:
 * $1 := s \left({0}\right)$
 * $2 := s \left({1}\right) = s \left({s \left({0}\right)}\right)$
 * $+$ denotes addition
 * $=$ denotes equality
 * $s \left({n}\right)$ denotes the successor function as defined by Peano