6 ideas
An illusion is a belief whose chief motive is wish-fulfilment, regardless of whether it happens to be true. It differs from an error, which is simply mistaken. It also differs from a delusion, which necessarily contradicts reality. What marks a belief as an illusion is its origin in desire, not its falsity, so a belief can be classified by its psychological source before its truth is settled.
Religious ideas arise from the adult's continued helplessness before nature, fate and death. That helplessness revives the child's longing for a powerful father who both threatens and protects. The gods are this father figure projected onto the cosmos, promising to tame nature's terrors, reconcile people to fate, and reward the renunciations civilisation demands.
Every culture must force individuals to give up instinctual satisfactions such as incest, cannibalism and murderous aggression, so each person is potentially an enemy of civilisation. Culture holds together through coercion and through ideals that compensate for these sacrifices. Religion has served as the most powerful of these compensations.
Religion can be read as a collective obsessional neurosis, like a child's neurosis rooted in the father complex. Just as children pass through neurotic phases, humanity may be expected to outgrow religion as it matures. Seen this way, religious ritual and dogma look like compulsive defences, and secularisation looks like a developmental stage rather than a loss.
When moral prohibitions such as "thou shalt not kill" are justified by divine command, they collapse for anyone who stops believing. Rules should instead be grounded in their rational social necessity, the shared human interest in living together. Then they survive the loss of faith and can be revised as needs change.
Scientific knowledge can correct itself through observation and experience, while religious doctrine forbids questioning and appeals to ancestral authority. The voice of the intellect is soft but persistent, and it gradually gains ground over the wish-driven mind. It would be an illusion to suppose that what science cannot give us can be obtained elsewhere.