Inferring the contrapositive from a universal negative proposition is invalid

Evidence

The appellant is taking the universal negative proposition, “No motile sperm are pre-11:11 (in terms of ejaculation)—No A is B—and attempting to infer the so-called contrapositive of that proposition, to wit, No non-motile sperm are post 11:11—(in purer terms, non-pre 11:11)—No non-A is non-B. By the laws of logic, however, the inference of the contrapositive is invalid where the starting proposition, as in the case at bar, is a universal negative.6 — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 907

Categorization

• DEFINE: XREF names what this plausibly connects to; SEED sketches the article/essay angle.
• corroborated: 2 independent passages support this claim — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 907
• XREF: connects to: Affirmative propositions leave their predicate term undistributed — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 404; Denying the antecedent assumes that if P implies Q, then non-P implies non-Q. — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 940; A universal proposition contains a distributed subject term while particular propositions are undistributed. — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 376

Broader Connections

• Affirmative propositions leave their predicate term undistributed #expands (0.55) — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 404
• Denying the antecedent assumes that if P implies Q, then non-P implies non-Q. #corroborates (0.35) — Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide to Clear…, 940