Full Idea
Aristotle believes cognition of particulars is more important for virtue than cognition of universals, ..and I would add that it is cognition not just of particulars, but of their value, that is, perception of them as good or beautiful.
Clarification
Universals are general ideas, rather than actual items in the world
Gist of Idea
It is not universals we must perceive for virtue, but particulars, seen as intrinsically good
Source
report of Aristotle (Nicomachean Ethics [c.334 BCE]) by Deborah Achtenberg - Cognition of Value in Aristotle's Ethics Intro
Book Reference
Achtenberg,Deborah: 'Cognition of Value in Aristotle's Ethics' [SUNY 2002], p.3
A Reaction
This gets quickly to the heart of the problem, which is what fact about the particular is perceived which makes it good. Utilitarians are queueing up to answer this question. Interesting, though.