To return to the arguments of rational morality. A man may say: "I don't care a bit about this social instinct you tell me of; I don't know that I possess it. It is no use your prating to me about my happiness of mind, and the necessity of my being in harmony with my surroundings. I prefer to gratify the instinct--the passion--that I do feel, regardless of the consequences to others. Of course, I shouldn't like everybody else to do the same. That is the beauty of my scheme, and I am not going to miss my opportunity in the short space of existence you tell me is all that lies before me. If it pleases me to make a beast of myself, I shall do so." All I can say is that a man who really means that this is what he would do, if not deterred by belief, is an unfortunate, with criminal tendencies--is, in fact, of unsound mind. His reasoning, too, is unsound. He must expect others to follow his example, as his argument is that the whole world would become immoral and lawless without belief. He would suffer, therefore, with the rest, and then would be the first, if sane, to co-operate with his fellow-sufferers in putting down lawlessness. The most savage tribe looks after its own interests according to its lights. A man who disregards the interest of all but himself becomes an Ishmael, an outlaw, a criminal; and, in the approaching Rationalistic age, he will be specially "taken care of," and treated as any other insane person. What are the causes of criminality? The Devil--man's sinful nature--the Religionist will reply. What does Science reply? Dr. McEwen, of Glasgow, relates in the Lancet how a labourer, after falling on his head from a scaffolding, developed immoral tendencies. A tumour had formed on his brain. This was successfully removed by trepanning, and the immoral tendencies disappeared. Again, Dr. Lydston tells us that Flesch examined the brains of fifty criminals, and found imperfections in all. "Vice and crime," says Dr. Lydston, "will one day be shown more definitely than ever to be a matter to be dealt with by medical science rather than by law." [327] When brain defects (whether inherited or caused by environment) affecting the moral faculties, are universally recognised as the real source of criminal tendencies; when disease of the brain is no longer regarded as a disease of the soul--then, and not till then, will criminality materially diminish. Science will triumphantly succeed where Religion has dismally failed.