Full Idea
It is not possible to say truly at the same time that the same thing both is and is not a man.
Gist of Idea
We cannot say that one thing both is and is not a man
Source
Aristotle (Metaphysics [c.324 BCE], 1006b33)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.92