Full Idea
Logos is for the purpose of clarifying the beneficial and the harmful and as a result the right and the wrong.
Gist of Idea
Reasoning distinguishes what is beneficial, and hence what is right
Source
Aristotle (Politics [c.332 BCE], 1253a12)
Book Reference
Aristotle: 'Politics', ed/tr. Sinclair,T.A. /Saunders,T. [Penguin 1992], p.60
A Reaction
I don't think this is asserting that reason can perceive values. Logos perceives the essential nature (and hence purpose) of each thing (including people), which indicates which are its good and bad states.