Full Idea
By form [eidos] I mean the essence [to ti en einai] of each thing and its primary being [prote ousia].
Gist of Idea
The form of a thing is its essence and its primary being
Source
Aristotle (Metaphysics [c.324 BCE], 1032b01)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.190
A Reaction
[Tr. Vasilis Politis. Lawson-Tancred has 'what-it-was-to-be-that-thing' instead of 'essence', and 'substance' instead of 'being']. This may be the single most important sentence in 'Metaphysics' for understanding his theory of being. Cf. 'formal cause'.