There is a theory of social development, sometimes called the materialistic interpretation of history, and sometimes the economic interpretation of history. It is one of the contributions to our thought which we owe to Karl Marx, and like all the rest of Marxian theory, it is a subject of embittered controversy, not merely between Socialists and orthodox economists, but between various schools of revolutionary doctrine. For my part, I have never been a great hand for doctrine, whether ancient or modern; I am not much more concerned with what Marx taught than I am with what St. Paul taught, or what Martin Luther taught. My advice is to look at life with your own eyes, and to state in simple language the conclusions of your own thinking. Man is an eating animal; he has also been described as a tool-making animal, and might be described as an ideal-making animal. There is a tendency on the part of those who specialize in the making of ideals to repudiate the eating and the tool-making sides of man; which accounts for the quarrel between the Marxians and the moralists. All through history you find new efforts of man to develop his emotional and spiritual nature, and to escape from the humiliating limitations of the flesh. These efforts have many of them been animated by desperate sincerity, but none of them have changed the fundamental fact that man is an eating animal, an animal insufficiently provided by nature against cold, and with an intense repugnance to having streams of cold water run down back of his neck. The religious teachers go out with empty purse, and "take no thought for the morrow"; but the forces of nature press insistently upon them, and little by little they make compromises, they take to shelter while they are preaching, they consent to live in houses, and even to own houses, and to keep a bank account. So they make terms with the powers of this world, and the powers of this world, which are subtle, and awake to their own interests, find ways to twist the new doctrine to their ends. So the new religion becomes simply another form of the old hypocrisy; and it comes to us as a breath of fresh air in a room full of corruption when some one says, "Let us have done with aged shams and false idealisms. Let us face the facts of life, and admit that man is a physical animal, and cannot do any sane and constructive thinking until he has food and shelter provided. Let us look at history with unblinking eyes, and realize that food and shelter, the material means of life, are what men have been seeking all through history, and will continue to seek, until we put production and distribution upon a basis of justice, instead of a basis of force."