The best and the worst things that men do they do in the name of a religion. Some have supposed that only supernatural religion could mislead. The history of our own time shows that if men no longer believe in God they will make themselves gods of Power, of Evolution, of the Race, the Nation, or the State. In the name of such gods will they drench a continent with blood, and the youth will offer themselves up as willing martyrs.

I think it's a problem that people are considered immoral if they're not religious. That's just not true. This might earn me some enemies, but in some ways they may be even more moral. If you do something for a religious reason, you do it because you'll be rewarded in an afterlife or in this world. That's not quite as good as something you do for purely generous reasons.

For good people to do evil doesn’t require only religion, or even any religion, but simply one of its key elements: belief without evidence—in other words, faith. And that kind of faith is seen not just in religion, but in any authoritarian ideology that puts dogma above truth and frowns on dissent.

The truth is that some people appear to be almost entirely motivated by their religious beliefs. Absent those beliefs, their behavior would make absolutely no sense; with them, it becomes perfectly understandable, even rational.

We keep on being told that religion, whatever its imperfections, at least instills morality. On every side, there is conclusive evidence that the contrary is the case and that faith causes people to be more mean, more selfish, and perhaps above all, more stupid.

Religion is an insult to human dignity. With or without it, you’d have good people doing good things and evil people doing evil things. But for good people to do evil things, it takes religion.

Having said all this to my friend, the priest Abdil, I went on: ‘And the most deplorable thing is that every man who destroys the existence of other beings in honor of his revered idols does so with all his heart, convinced beyond any doubt that he is doing a “good deed.” ‘If any one of them should become aware that in destroying the existence of another being he is not only committing an evil deed against the true God and every real saint, but is even causing them, in their essence, sorrow and grief that there should exist in the Great Universe such monsters made “in the image of God,” who can manifest themselves so ruthlessly and without conscience toward other creatures of our Common Father — I repeat, if any one of them should become aware of this, he would certainly agree with all his heart never again to destroy the existence of beings of other forms for sacrificial offerings.

A bad action is always bad at the time when it is done, no matter what happens afterwards. Every time we let ourselves believe for unworthy reasons, we weaken our powers of self-control, of doubting, of judicially and fairly weighing evidence. We all suffer severely enough from the maintenance and support of false beliefs and the fatally wrong actions which they lead to, and the evil born when one such belief is entertained is great and wide. But a greater and wider evil arises when the credulous character is maintained and supported, when a habit of believing for unworthy reasons is fostered and made permanent. If I steal money from any person, there may be no harm done from the mere transfer of possession; he may not feel the loss, or it may prevent him from using the money badly. But I cannot help doing this great wrong towards Man, that I make myself dishonest. What hurts society is not that it should lose its property, but that it should become a den of thieves, for then it must cease to be society. This is why we ought not to do evil, that good may come; for at any rate this great evil has come, that we have done evil and are made wicked thereby. In like manner, if I let myself believe anything on insufficient evidence, there may be no great harm done by the mere belief; it may be true after all, or I may never have occasion to exhibit it in outward acts. But I cannot help doing this great wrong towards Man, that I make myself credulous. The danger to society is not merely that it should believe wrong things, though that is great enough; but that it should become credulous, and lose the habit of testing things and inquiring into them; for then it must sink back into savagery.

Religion is an insult to human dignity. With or without it you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion.

One of the enduring pathologies of human culture is the tendency to raise children to fear and demonize other human beings on the basis of religious faith. Consequently, faith inspires violence in at least two ways. First, people often kill other human beings because they believe that the creator of the universe wants them to do it. Islamist terrorism is a recent example of this sort of behavior. Second, far greater numbers of people fall into conflict with one another because they define their moral community on the basis of the religious affiliation: Muslims side with other Muslims, Protestants with Protestants, Catholics with Catholics. These conflicts are not always explicitly religious. But the bigotry and hatred that divide one community from another are often the products of their religious identities.

Mais, monsieur, en étant persuadés par la foi, des choses qui paraissent absurdes à notre intelligence, c'est-à-dire, en croyant ce que nous ne croyons pas, gardons-nous de faire ce sacrifice de notre raison dans la conduite de la vie. Il y a eu des gens qui ont dit autrefois: Vous croyez des choses incompréhensibles, contradictoires, impossibles, parce que nous vous l'avons ordonné; faites donc des choses injustes parce que nous vous l'ordonnons. Ces gens-là raisonnaient à merveille. Certainement qui est en droit de vous rendre absurde est en droit de vous rendre injuste. Si vous n'opposez point aux ordres de croire l'impossible l'intelligence que Dieu a mise dans votre esprit, vous ne devez point opposer aux ordres de malfaire la justice que Dieu a mise dans votre coeur. Une faculté de votre âme étant une fois tyrannisée, toutes les autres facultés doivent l'être également. Et c'est là ce qui a produit tous les crimes religieux dont la terre a été inondée.

I’m not blaming religion for all or even most human barbarism. Of course faith in God generates compassion and altruism as well. Religious belief probably motivated some rescue workers who tried so heroically to save people from the wreckage. Religious belief offers solace and strength to people in the awful aftermath of the attack. But while they gather together to pray and seek comfort, protection, or approval from God, so do the terrorists. Whatever lessons we take from this dreadful attack, we should never forget that it was, after all, a faith based initiative.

There is a dark side to religious devotion that is too often ignored or denied. As a means of motivating people to be cruel or inhumane, there may be no more potent force than religion. When the subject of religiously inspired bloodshed comes up, many Americans immediately think of Islamic fundamentalism, which is to be expected in the wake of 911. But men have been committing heinous acts in the name of God ever since mankind began believing in deities, and extremists exist within all religions. Muhammad is not the only prophet whose words have been used to sanction barbarism; history has not lacked for Christians, Jews, Hindus, Sikhs, and even Buddhists who have been motivated by scripture to butcher innocents. Plenty of these religious extremist have been homegrown, corn-fed Americans.

Because most religions conceive of morality as a matter of being obedient to the word of God (generally for the sake of receiving a supernatural reward), their precepts often have nothing to do with maximizing well-being in this world. Religious believers can, therefore, assert the immorality of contraception, masturbation, homosexuality, etc., without ever feeling obliged to argue that these practices actually cause suffering. They can also pursue aims that are flagrantly immoral, in that they needlessly perpetuate human misery, while believing that these actions are morally obligatory. This pious uncoupling of moral concern from the reality of human and animal suffering has caused tremendous harm.