Monomania is essentially a disease of the sensibility. It reposes altogether upon the affections, and its study is inseparable from a knowledge of the passions. Its seat is in the heart of man, and it is there that we must search for it, in order to possess ourselves of all its peculiarities. How many are the cases of monomania caused by thwarted love, by fear, vanity, wounded self-love, or disappointed ambition.