He who knows only his own side of the case, knows little of that. His reasons may be good, and no one may have been able to refute them. But if he is equally unable to refute the reasons on the opposite side; if he does not so much as know what they are, he has no ground for preferring either opinion.
John Stuart Mill
Good video of Jonathan Haidt, founder of Heterodox Academy, on viewpoint diversity and the need for institutional disconfirmation in universities: