[Freud's] sense of reality is less clouded by wishful thinking than is the case with other people and [he combines] the qualities of critical judgment, earnestness and responsibility.
But there is another reason for the high repute of mathematics: it is mathematics that offers the exact natural sciences a certain measure of security which, without mathematics, they could not attain.
A human being is a part of the whole called by us universe; a part limited in time and space. He experiences himself, his thoughts, and his feelings as something separate from the rest - a kind of optical delusion of consciousness.