"A dead man is not a man": Geach's implicature

Speranza

"Logic matters", p. 17.

Geach's example.

Paul is a cobbler.
Paul is good.
----
Therefore, Paul is a good cobbler.

FALLACIOUS.

Paul is a man.
Paul is dead.
---
Therefore, Paul is a dead man.

FALLACIOUS.

Geach: "A dead man is not a man."