The ideal, without doubt, varies, but its enemies, alas, are always the same.

We are not naïve enough to ask for pure men; we ask merely for men whose impurity does not conflict with the obligations of their job.

Theories pass. The frog remains.

Science had better not free the minds of men too much, before it has tamed their instincts.

I think I am one of those who can manage not to take on a completely different appearance under their own glance.

It may offend us to hear our own thoughts expressed by others: we are not sure enough of their souls.

Take heed of critics even when they are not fair; resist them even when they are.