Full Idea
We think friendship is the greatest good for cities, since this way people are least likely to engage in faction.
Gist of Idea
Friendship is the best good for cities, because it reduces factions
Source
Aristotle (Politics [c.332 BCE], 1262b07)
Book Reference
Aristotle: 'Politics', ed/tr. Reeve,C.D.C. [Hackett 2017], p.25
A Reaction
Earlier philosophers were deeply worried about 'faction', but we now accept the gangs of secretive hoodlums called political parties. I suspect the old view was right, but it's a bit late now. You can't engineer friendships (can you?).