Religion has ever filled the mind of man with darkness, and kept him in ignorance of his real duties and true interests. It is only by dispelling the clouds and phantoms of Religion, that we shall discover Truth, Reason, and Morality. Religion diverts us from the causes of evils, and from the remedies which nature prescribes; far from curing, it only aggravates, multiplies, and perpetuates them.

I think that you cannot eliminate religion from the psyche of mankind. If you suppress it in one form, it merely emerges in another form. Even if you don't believe in God, you still have to believe in something that gives meaning to your life, and shapes your sense of the world. Such a belief is religious.

One of the most pernicious effects of religion is that it tends to divorce morality from the reality of human and animal suffering. Religion allows people to imagine that their concerns are moral when they are not — that is, when they have nothing to do with suffering or its alleviation. Indeed, religion allows people to imagine that their concerns are moral when they are highly immoral — that is, when pressing these concerns inflicts unnecessary and appalling suffering on innocent human beings.

Religion suppresses curiosity.

Religion has had the disastrous effect of placing vitally important concepts, such as morality, happiness and love, in a supernatural realm inaccessible to man’s mind and knowledge.

Religion has clearly performed great services for human civilization. It has contributed much towards the taming of the asocial instincts. But not enough. It has ruled human society for many thousands of years and has had time to show what it can achieve. If it had succeeded in making the majority of mankind happy, in comforting them, in reconciling them to life and in making them into vehicles of civilization, no one would dream of attempting to alter the existing conditions. But what do we see instead? We see that an appallingly large number of people are dissatisfied with civilization and unhappy in it, and feel it as a yoke which must be shaken off; and that these people either do everything in their power to change that civilization, or else go so far in their hostility to it that they will have nothing to do with civilization or with a restriction of instinct. At this point it will be objected against us that this state of affairs is due to the very fact that religion has lost a part of its influence over human masses precisely because of the deplorable effect of the advances of science. We will note this admission and the reason given for it, and we shall make use of it later for our own purposes; but the objection itself has no force.

It is doubtful whether men were in general happier at a time when religious doctrines held unrestricted sway; more moral they certainly were not. They have always known how to externalize the precepts of religion and thus to nullify their intentions. The priests, whose duty it was to ensure obedience to religion, met them half-way in this. God's kindness must lay a restraining hand on His justice. One sinned, and then one made a sacrifice or did penance and then one was free to sin once more. Russian introspectiveness has reached the pitch of concluding that sin is indispensable for the enjoyment of all the blessings of divine grace, so that, at bottom, sin is pleasing to God. It is no secret that the priests could only keep t

Religion is a psychic disease of the brain.

The foundation of irreligious criticism is: Man makes religion, religion does not make man. Religion is, indeed, the self-consciousness and self-esteem of man who has either not yet won through to himself, or has already lost himself again. But man is no abstract being squatting outside the world. Man is the world of man – state, society. This state and this society produce religion, which is an inverted consciousness of the world, because they are an inverted world...

Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.

The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo.

Criticism has plucked the imaginary flowers on the chain not in order that man shall continue to bear that chain without fantasy or consolation, but so that he shall throw off the chain and pluck the living flower. The criticism of religion disillusions man, so that he will think, act, and fashion his reality like a man who has discarded his illusions and regained his senses, so that he will move around himself as his own true Sun. Religion is only the illusory Sun which revolves around man as long as he does not revolve around himself.

Religious suffering is, at one and the same time, the expression of real suffering and protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people. The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo. Criticism has plucked the imaginary flowers on the chain not in order that man shall continue to bear that chain without fantasy or conclusion, but so that he shall throw off the chain and pluck the living flower.

Religion grants its adherents malign, intoxicating and morally corrosive sensations. Destroying intellectual freedom is always evil, but only religion makes doing evil feel quite so good.

What’s the use of religion if it oppresses instead of consoling? If it offers despair instead of relief? If it takes away instead of preserving?

What worries me about religion is that it teaches people to be satisfied with not understanding the world they live in.

one of the truly bad effects of religion is that it teaches us that it is a virtue to be satisfied with not understanding.

There certainly seems to be a strong correlation between religion and insanity. I’ve read a few papers comparing the logical and psychological aptitude of strong believers vs those with little or no faith at all, and the trends there all seem to be in our favor, but not to the point that religion causes the disorder. I think certain mental disorders can prompt religious beliefs, but that’s a different claim. I think religion provides a haven to conceal quite a lot of cognitive and psychiatric disorders as well as some social dysfunctions. But that doesn’t mean religion is a mental illness, regardless how accurate analogies of the God virus might be. I think there are circumstances when religion can be treated as a psychological condition, especially when it is the result of detrimental conditioning, but I wouldn’t confuse that with a psychiatric malady, which (I think) would have to be physiological/chemical.