Discourses: Book 1 5 : 2

Now there are two kinds of petrifaction: one is the petrifaction of the intellect, the other of the sense of shame, when a man stands in array, prepared neither to assent to manifest truths nor to leave the fighting line. Most of us dread the deadening of the body and would resort to all means so as to avoid falling into such a state, but about the deadening of the soul we care not at all. Indeed, by Zeus, even in the case of the soul itself, if a man be in such a state that he cannot follow an argument step by step, or even understand one, we regard him too as being in a bad way; but if a man's sense of shame and self-respect be deadened, this we go so far as to call strength of character!