I haven't a particle of confidence in a man who has no redeeming petty vices whatsoever. - Vicesimus Knox

O philosophy, life’s guide! O searcher-out of virtue and expeller of vices! What could we and every age of men have been without thee?

The problem with people who have no vices is that generally you can be pretty sure they're going to have some pretty annoying virtues.

We must carefully teach children to detest vices for what they consist in; we must teach them their natural ugliness, so that they flee them not only in their deeds but in their minds: the very thought of them should be hateful, whatever mask they hide behind.