Full Idea
There cannot be demonstrations that this particular triangle is equal to the sum of two right angles, except that every triangle is equal to the sum of two right angles, nor that this particular man is an animal, except that every man is an animal.
Gist of Idea
Demonstrations about particulars must be about everything of that type
Source
Aristotle (Metaphysics [c.324 BCE], 1086b36)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.427
A Reaction
Not quite the covering-law model, but well on the way. Why can't we demonstrate that this particular is different from the others? This tiger is docile; this butterfly stings. We just like generalisations because you know more with less effort.