Description: The specialization axiom of standard predicate calculus. It states that
if a statement ph holds for all x , then it also holds for the
specific case of t (properly) substituted for x . Translated to
traditional notation, it can be read: " A. x ph ( x ) -> ph ( t ) ,
provided that t is free for x in ph ( x ) ". Axiom 4 of
Mendelson p. 69. See also spsbc and rspsbc . (Contributed by NM, 14-May-1993) Revise df-sb . (Revised by BJ, 22-Dec-2020)