Now, some Mohammedans are the crudest in this respect, and the most sectarian. Their watch-word is: "There is one God, and Mohammed is His Prophet." Everything beyond that not only is bad, but must be destroyed forthwith, at a moment’s notice, every man or woman who does not exactly believe in that must be killed; everything that does not belong to this worship must be immediately broken; every book that teaches anything else must be burnt. From the Pacific to the Atlantic, for five hundred years blood ran all over the world. That is Mohammedanism. Nevertheless, among these Mohammedans, wherever there has a philosophic man, he was sure to protest against these cruelties. In that he showed the touch of the Divine and realised a fragment of the truth; he was not playing with his religion; for it was not his father's religion he was talking, but spoke the truth direct like a man.
The more selfish a man, the more immoral he is. And so also with the race. That race which is bound down to itself has been the most cruel and the most wicked in the whole world. There has not been a religion that has clung to this dualism more than that founded by the Prophet of Arabia, and there has not been a religion, which has shed so much blood and been so cruel to other men. In the Koran there is the doctrine that a man who does not believe these teachings should be killed, it is a mercy to kill him! And the surest way to get to heaven, where there are beautiful houris and all sorts of sense enjoyments, is by killing these unbelievers. Think of the bloodshed there has been in consequence of such beliefs! 
Why religions should claim that they are not bound to abide by the standpoint of reason, no one knows. If one does not take the standard of reason, there cannot be any true judgment, even in the case of religions. One religion may ordain something very hideous. For instance, the Mohammedan religion allows Mohammedans to kill all who are not of their religion. It is clearly stated in the Koran, Kill the infidels if they do not become Mohammedans. They must be put to fire and sword. Now if we tell a Mohammedan that this is wrong, he will naturally ask, "How do you know that? How do you know it is not good? My book says it is."