Full Idea
There must be more than one soul (not fewer than two) controlling movement and the heavens: that which does good, and that which has the opposite capacity.
Gist of Idea
There must be at least two souls controlling the cosmos, one doing good, the other the opposite
Source
Plato (The Laws [c.349 BCE], 896e)
Book Reference
Plato: 'Complete Works', ed/tr. Cooper,John M. [Hackett 1997], p.1553
A Reaction
[Wording compressed - as often with the dialogues] This idea of controlling opposites is found in Empedocles. Presumably this good soul defers to the Form of the Good, as implied by the Euthyphro Question.
Related Idea
Idea 552 Empedocles said good and evil were the basic principles [Empedocles, by Aristotle]