Full Idea
It is when we know what a man is or what fire is that we reckon that we know a particular item in the fullest sense, rather than when we merely know its quality, quantity or location.
Gist of Idea
We know something when we fully know what it is, not just its quality, quantity or location
Source
Aristotle (Metaphysics [c.324 BCE], 1028a36)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.168
A Reaction
The word 'what' should usually be taken to indicate that Aristotle is talking about essence (as V. Politis confirms of this passage). This idea is a key one for the claim that Aristotelian essences are essentially (sic) explanatory.