It is a mistake to believe that science consists in nothing but conclusively proved propositions, and it is unjust to demand that it should. It is a demand made by those who feel a craving for authority in some form to replace the religious catechism by something else, even a scientific one.

Religious doctrines … are all illusions, they do not admit of proof, and no one can be compelled to consider them as true or to believe in them.

No one who has seen a baby sinking back satiated from the breast and falling asleep with flushed cheeks and a blissful smile can escape the reflection that this picture persists as a prototype of the expression of sexual satisfaction in later life.

Civilized society is perpetually menaced with disintegration through this primary hostility of men towards one another.

Just as a satisfaction of instinct spells happiness for us, so severe suffering is caused us if the external world lets us starve, if it refuses to sate our needs. One may therefore hope to be freed from a part of one's sufferings by influencing the instinctual impulses.

The state in which the ideas existed before being made conscious is called by us repression, and we assert that the force which instituted the repression and maintains it is perceived as resistance during the work of analysis.

I no longer count as one of my merits that I always tell the truth as much as possible; it has become my metier.