If you paid attention in Logic 101 you may remember that the immediate inference called 'conversion' is valid for the I and E forms of the traditional square of opposition but not for the A and O forms. Poetic illustration courtesy of Alexander Pope (1688-1744) where 'Every poet is a fool' is an A-proposition:
Sir, I admit your gen'ral rule
That every poet is a fool:
But you yourself may serve to show it,
That every fool is not a poet.
(Epigrams and Epitaphs, Faber & Faber, 1977, p. 82)