Full Idea
The rule is that when one perceives first the community between the members of a group of many things, one should not desist until one sees in it all those differences that are located in classes.
Gist of Idea
Whenever you perceive a community of things, you should also hunt out differences in the group
Source
Plato (The Statesman [c.356 BCE], 285b)
Book Reference
Plato: 'Complete Works', ed/tr. Cooper,John M. [Hackett 1997], p.328
A Reaction
He goes on to recommend the opposite as well - see community even when there appears to be nothing but differences. I take this to be analysis, just as much as modern linguistic approaches are. Analyse the world, not language.