Full Idea
Anaxagoras says the good is a principle as the source of movement, in the form of Mind. However it does it for the sake of something else, which is a further factor. And he allows no opposite to the good Mind.
Gist of Idea
For Anaxagoras the Good Mind has no opposite, and causes all movement, for a higher reason
Source
report of Anaxagoras (fragments/reports [c.460 BCE]) by Aristotle - Metaphysics 1075b
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.387