“If we believe the Christian religion, our notions of what is good will be different from what they will be if we do not believe it. Therefore to Christians the effects of Christianity may seem good, while to unbelievers they may seem bad. Moreover, the attitude that one ought to believe such and such a proposition, independently of the question whether there is evidence in its favour, is an attitude which produces hostility to evidence and causes us to close our minds to every fact that does not suit our prejudices.
A certain kind of scientific candour is a very important quality, and it is one which can hardly exist in a man who imagines that there are things which it is his duty to believe.

– Bertrand Russel, Has religion made useful contributions to civilisation?