Full Idea
It is an essential [kath' auto] property of man to be 'by nature a civilized animal'.
Clarification
'Kath' auto' really means 'intrinsic' or 'per se'
Gist of Idea
Man is intrinsically a civilized animal
Source
Aristotle (Topics [c.331 BCE], 128b17)
Book Reference
Aristotle: 'Posterior Analytics and Topica', ed/tr. Tredennick,H/Forster,ES [Harvard 1960], p.481
A Reaction
I take this, along with man being intrinsically rational, to be the foundation of Aristotelian ethics. Given that we are civilized, self-evident criteria emerge for how to be good at it. A good person is, above all, a good citizen.