Full Idea
The part of a contradictory pair which says something of something is an affirmation; the part which takes something from something is a negation.
Gist of Idea
Negation takes something away from something
Source
Aristotle (Posterior Analytics [c.327 BCE], 72a14)
Book Reference
Aristotle: 'Posterior Analytics (2nd ed)', ed/tr. Barnes,Jonathan [OUP 1993], p.3
A Reaction
So affirmation is predication about an object ['Fa'], and negation is denial of predication. We have a scope problem: there is nothing which is F [¬∃x(Fx)], or there is a thing which is not-F [∃x(¬Fx)]. Aristotle seems to mean the latter.