**Description: **Principle of identity.
Theorem *2.08 of [WhiteheadRussell] p.
101. This
version is proved directly from the axioms for demonstration purposes.
This proof is a popular example in the literature and is identical, step
for step, to the proofs of Theorem 1 of [Margaris] p. 51, Example 2.7(a)
of [Hamilton] p. 31, Lemma 10.3 of [BellMachover] p. 36, and Lemma 1.8 of
[Mendelson] p. 36. It is also "Our
first proof" in Hirst and Hirst's *A
Primer for Logic and Proof* p. 17 (PDF p. 23) at
http://www.mathsci.appstate.edu/~jlh/primer/hirst.pdf.
For a shorter
version of the proof that takes advantage of previously proved theorems,
see id 19. (Contributed by NM, 5-Aug-1993.) Use id 19
instead.
(New usage is discouraged.) |