Madness.

There is no greatness without a continual solicitation to madness which, while it must be overcome, must never be completely lacking. One might profit by classifying men in this respect. The one kind are those in whom there is no madness at all and are so-called men of intellect whose works and deeds are nothing but cold works and deeds of the intellect.  But where there is no madness, there is, to be sure, also no real, active, living intellect. For wherein is intellect to prove itself but in the conquest, mastery, and ordering of madness?

Friedrich Schelling