Full Idea
The definition ought to be peculiar to one thing, not common to many.
Gist of Idea
The definition is peculiar to one thing, not common to many
Source
Aristotle (Topics [c.331 BCE], 149b24)
Book Reference
Aristotle: 'Posterior Analytics and Topica', ed/tr. Tredennick,H/Forster,ES [Harvard 1960], p.633
A Reaction
I take this to be very important, against those who think that definition is no more than mere categorisation. To explain, you must get down to the level of the individual. We must explain that uniquely docile tiger.