The fact is you cannot be intelligent merely by choosing your opinions

From Mortals and Others by Bertrand Russell.

The fact is you cannot be intelligent merely by choosing your opinions. The intelligent man is not the man who holds such-and-such views but the man who has sound reasons for what he believes and yet does not believe it dogmatically. And opinions held for sounds reason have less emotional unity than the opinions of dogmatists because reason is non-party, favouring now one side and now another. That is what people find so unpleasant about it. In education, pupils ought to be made to admit one unpleasant opinion everyday, and no person whose views form a self-consistent whole should be allowed to teach. Then, perhaps, the virulence of orthodoxies might diminish.