|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. 16 (PDF p. 22) at
For a shorter
version of the proof that takes advantage of previously proved theorems,
see id 15.|