Full Idea
It is legitimate to play the devil's advocate.
Clarification
A 'devil's advocate' deliberately argues for something they don't believe
Gist of Idea
It is legitimate to play the devil's advocate
Source
Socrates (reports of career [c.420 BCE]), quoted by Plato - Phaedrus 272c
Book Reference
Plato: 'Phaedrus and Letters VII and VIII', ed/tr. Hamilton,Walter [Penguin 1973], p.93