The view is often defended that sciences should be built up on clear and sharply defined basal concepts. In actual fact no science, not even the most exact, begins with such definitions. The true beginning of scientific activity consists rather in describing phenomena and then in proceeding to group, classify and correlate them.

The pleasure of satisfying a savage instinct, undomesticated by the ego, is uncomparably much more intense than the one of satisfying a tamed instinct. The reason is becoming the enemy that prevents us from a lot of possibilities of pleasure.

It could be ventured to understand obsessive compulsive neurosis as the pathological counterpart of religious development, to define neurosis as an individual religiosity; to define religion as a universal obsessive compulsive neurosis.

The inclination to aggression constitutes the greatest impediment to civilization.

Indeed, the great Leonardo (da Vinci) remained like a child for the whole of his life in more than one way. It is said that all great men are bound to retain some infantile part. Even as an adult he continued to play, and this was another reason why he often appeared uncanny and incomprehensible to his contemporaries.

Knowledge is the intellectual manipulation of carefully verified observations.

A religion, even if it calls itself a religion of love, must be hard and unloving to those who do not belong to it.