2 For the proof to be rigorous, a formal language L for Peano Arithmetic should be specified in full. L is a first-order predicate calculus in universally quantified free variable form. The syntax of L will specify as usual the terms and formulas of L, the formula ‘P(r)’ in the term ‘r’,and the result ‘P(t)’ of substituting the term ‘t’ for the occurrences of ‘r’ in ‘P(r)' (sometimes written P(r)[r/t]). It should also be mentioned that a modernized form of the Peano