When one does not have what one wants, one must want what one has.

Demons do not exist any more than gods do, being only the products of the psychic activity of man.

Only the real, rare, true scientific minds can endure doubt, which is attached to all our knowledge.

The most complicated achievements of thought are possible without the assistance of consciousness.

Instinct of love toward an object demands a mastery to obtain it, and if a person feels they can't control the object or feel threatened by it, they act negatively toward it.

I've been a fortunate man in life, nothing has come easily.

I cannot think of any need in childhood as strong as the need for a father's protection.