Sigmund Freud is the father of psychoanalysis, massively influential. He was led into the field of psychoanalysis by his opposition to religion. Freud believed that religion was a great hindrance to society, and so set out to prove that it is merely a product of the mind, an illusion. He offered both a psychological and a historical explanation of the origins of religion.

Freud’s historical explanation of religion is set out in his Totem and Taboo. There he imagines a father of a primal horde, whose sons envy his access to the tribe’s women, and so overwhelm and kill him. Even after their rebellion, the sons cannot fulfil their desire to emulate their father, due to competition between them. Religion arose out of the frustration and guilt that they felt.

Freud’s psychological explanation of religion builds on the ideas of Ludwig Feuerbach. Feuerbach developed the idea that God is projection of the unconscious mind; Freud added to this a psychological foundation. For Freud, as for Feuerbach, religion is wish-fulfilment. Freud adds the explanation that the adoption of religion is a reversion to childish patterns of thought in response to feelings of helplessness and guilt. We feel a need for security and forgiveness, and so invent a source of security and forgiveness: God. Religion is thus seen as a childish delusion, and atheism as a grown-up realism.