The man who imagines a social system as a tree will have a different political outlook. A bad machine can be scrapped, and another put in its place. But if a tree is cut down, it is a long time before a new tree achieves the same strength and size. A machine or a mould is what its maker chooses; a tree has its specific nature, and can only be made into a better or worse example of the species. Constructiveness applied to living things is quite different from constructiveness applied to machines; it has humbler functions, and requires a sort of sympathy. For that reason, in teaching constructiveness to the young, they should have opportunities of exercising it upon plants and animals, not only upon bricks and machines. Physics has been dominant in thought since the time of Newton, and in practice since the industrial revolution; this has brought with it a rather mechanical conception of society. Biological evolution introduced a new set of ideas, but they were somewhat overshadowed by natural selection, which it should be our aim to eliminate from human affairs by eugenics, birth-control, and education. The conception of society as a tree is better than the mould or the machine, but it is still defective. It is to psychology that we must look to supply the deficiency. Psychological constructiveness is a new and special kind, very little understood as yet. It is essential to a right theory of education, politics, and all purely human affairs. And it should dominate the imaginations of citizens, if they are not to be misled by false analogies. Some people dread constructiveness in human affairs, because they fear that it must be mechanical; they therefore believe in anarchism and the “return to nature”. I am trying in this book to show, in concrete instances, how psychological construction differs from the construction of a machine. The imaginative side of this idea ought to be made familiar in higher education; if it were, I believe that our politics would cease to be angular and sharp and destructive, becoming instead supple and truly scientific, with the development of splendid men and women as its goal. CHAPTER VII SELFISHNESS AND PROPERTY I come now to a problem analogous to that of Fear, in that we are concerned with an impulse which is strong, partly instinctive, and largely undesirable. In all such cases, we have to be careful not to thwart a child’s nature. It is useless to shut our eyes to his nature, or to wish that it were different; we must accept the raw material which is provided, and not attempt to treat it in ways only applicable to some different material.