| Description: Deduction introducing an
embedded antecedent. (The proof was revised by
Stefan Allan, 20-Mar-2006.)
Naming convention: We often call a theorem a
"deduction" and suffix
its label with "d" whenever the hypotheses and conclusion are
each
prefixed with the same antecedent. This allows us to use the theorem in
places where (in traditional textbook formalizations) the standard
Deduction Theorem would be used; here would be replaced with a
conjunction (df-an 225) of the hypotheses of the would-be deduction.
By
contrast, we tend to call the simpler version with no common antecedent
an "inference" and suffix its label with "i";
compare theorem a1i 8.
Finally, a "theorem" would be the form with no hypotheses; in
this case
the "theorem" form would be the original axiom ax-1 4.
In
propositional calculus we usually prove the theorem form first without a
suffix on its label (e.g. pm2.43 63 vs. pm2.43i 64 vs. pm2.43d 65), but
(much) later we often suffix the theorem form's label with "t"
as in
negnegt 5405 vs. negneg 5402, especially when our "weak deduction
theorem"
dedth 2387 is used to prove the theorem form from its
inference form. When
an inference is converted to a theorem by eliminating an "is a
set"
hypothesis, we sometimes suffix the theorem form with "g" (for
somewhat
overstated "generalized") as in uniex 2876 vs. uniexg 2877. |