Full Idea
Things are alike if they are not just the same simpliciter, exhibiting differences in their substrate substance but being formally the same. Examples are larger and smaller quadrangles and unequal straight lines, which are alike but not the same.
Gist of Idea
Things such as two different quadrangles are alike but not wholly the same
Source
Aristotle (Metaphysics [c.324 BCE], 1054b06)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.294