Full Idea
There are falsehoods which are contrary to one another and cannot be the case together e.g. that a man is a horse or a cow.
Gist of Idea
Two falsehoods can be contrary to one another
Source
Aristotle (Posterior Analytics [c.327 BCE], 88a29)
Book Reference
Aristotle: 'Posterior Analytics (2nd ed)', ed/tr. Barnes,Jonathan [OUP 1993], p.44