From the Prior Analytics (Aristotle, Book ch 13):"[W]e say that the necessary is contingent [endekhomenon]". As an online site has it, this may sound as"paradoxical" ...
I believe you are talking about De Interpretatione, 12 ad 13. Why, is not exactly clear.
Robert Paul ------------------------------------------------------------------ To change your Lit-Ideas settings (subscribe/unsub, vacation on/off, digest on/off), visit www.andreas.com/faq-lit-ideas.html