Full Idea
The chief good is to live in perfect indifference to all those things which are of an intermediate character between virtue and vice.
Gist of Idea
The chief good is indifference to what lies midway between virtue and vice
Source
report of Ariston (fragments/reports [c.250 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 07.2.1
Book Reference
Diogenes Laertius: 'Diogenes Laertius', ed/tr. Yonge,C.D. [Henry G. Bohn 1853], p.318