|Description: Axiom Transp.
Axiom A3 of [Margaris] p. 49. One of the 3
propositional calculus. It swaps or "transposes" the order of
consequents when negation is removed. An informal example is that the
statement "if there are no clouds in the sky, it is not raining"
the statement "if it is raining, there are clouds in the sky."
is called Transp or "the principle of transposition" in
Mathematica (Theorem *2.17 of [WhiteheadRussell] p. 103). We will also
use the term "contraposition" for this principle, although the
advised that in the field of philosophical logic,
"contraposition" has a
different technical meaning. (Contributed by NM, 30-Sep-1992.) Use its
alias con4 109 instead. (New usage is