Consider the Koran, for example; this wretched book was sufficient to start a world-religion, to satisfy the metaphysical need of countless millions for twelve hundred years, to become the basis of their morality and of a remarkable contempt for death, and also to inspire them to bloody wars and the most extensive conquests. In this book we find the saddest and poorest form of theism. Much may be lost in translation, but I have not been able to discover in it one single idea of value.
— Arthur Schopenhauer
But would we know, whether the pretended prophet had really attained a just sentiment of morals? Let us attend to his narration; and we shall soon find, that he bestows praise on such instances of treachery, inhumanity, cruelty, revenge, bigotry, as are utterly incompatible with civilized society. No steady rule of right seems there to be attended to; and every action is blamed or praised, so far only as it is beneficial or hurtful to the true believers.
— David Hume
I studied the Quran a great deal. I came away from that study with the conviction that by and large there have been few religions in the world as deadly to men as that of Muhammad. As far as I can see, it is the principal cause of the decadence so visible today in the Muslim world and, though less absurd than the polytheism of old, its social and political tendencies are in my opinion more to be feared, and I therefore regard it as a form of decadence rather than a form of progress in relation to paganism itself.
— Alexis de Tocqueville
Muslims are the first victims of Islam. Many times I have observed in my travels in the Orient that fanaticism comes from a small number of dangerous men who maintain the others in the practice of religion by terror. To liberate the Muslim from his religion is the best service one can render him.
— Ernest Renan