Syntax Definition wi 4

Description: If ph and ps are wff's, so is ( ph -> ps ) or " ph implies ps". Part of the recursive definition of a wff. The left-hand wff is called the antecedent, and the right-hand wff is called the consequent. In the case of ( ph -> ( ps -> ch ) ), the middle ps may be informally called either an antecedent or part of the consequent depending on context.

Hypotheses

Ref	Expression
wph	wff ph
wps	wff ps

Assertion

Ref	Expression
wi	wff ( ph -> ps )

This syntax is primitive. The first axiom using it is ax-1 6.