Evidently, however, there is something in man which rebels against these "natural" laws. In our present society man has set aside six days in the week in which to live under them, and one day in the week in which to preach an entirely different and contradictory code--that of Christian ethics, which bids you "love your neighbor," and "do unto others as you would they should do unto you." Between these Sunday teachings and the week-day teachings there is eternal conflict, and one who takes pleasure in ridiculing his fellow men can find endless opportunity here. The Sunday preachers are forbidden to interfere with the affairs of the other six days; that is called "dragging politics into the pulpit." On the other hand, incredible as it may seem, there are professors of the week-day doctrine who call themselves Christians, and believe in the Sunday doctrine, too. They manage this by putting the Sunday doctrine off into a future world; that is, we are to pounce upon one another and devour one another under the "iron laws" of economics so long as we live on earth, but in the next world we shall play on golden harps and have nothing to do but love one another. If anybody is so foolish as to apply the Sermon on the Mount to present-day affairs, we regard him as a harmless crank; if he persists, and sets out to teach others, we call him a Communist or a Pacifist, and put him in jail for ten or twenty years. In the Book of the Mind, I have referred to Kropotkin's "Mutual Aid as a Factor in Evolution," which I regard as one of the epoch-making books of our time. Kropotkin clearly proves that competition is not the only law of nature, it is everywhere modified by co-operation, and in the great majority of cases co-operation plays a larger part in the relations of living creatures than competition. There is no creature in existence which is entirely selfish; in the nature of the case such a creature could not exist--save in the imaginations of teachers of special privilege. If a species is to survive, some portion of the energies of the individual must go into reproduction; and steadily, as life advances, we find the amount of this sacrifice increasing. The higher the type of the creature, the longer is the period of infancy, and the greater the sacrifice of the parent for the young. Likewise, most creatures make the discovery that by staying together in herds or groups, and learning to co-operate instead of competing among themselves, they increase their chances of survival. You find birds that live in flocks, and other birds, like hawks and owls and eagles, that are solitary; and you find the co-operating birds a thousand times as numerous--that is to say, a thousand times as successful in the struggle for survival. You find that all man's brain power has been a social product; the supremacy he has won over nature has depended upon one thing and one alone--the fact that he has managed to become different