Is thinking and imagining a kind of insanity?

The irrational in the human has something about it altogether repulsive and terrible, as we see in the maniac, rapist, the miser, the drunkard or the beast. Humans are endowed with intellect and capacity to use reason to control emotions and harmonize them with intelligence. A person overwhelmed by base emotions, or mental disease or by instincts often indulges in acts or utter words that create the impression of insanity.