Now we notice that the cube _has_ surfaces and so _has certain surface properties_. Do we, therefore, say that a solid _is_ a surface? That the cube is a member of the class of surfaces? If we did, we should be fools—type-confusing fools—dimension-mixing fools. That is evident. Or suppose we notice that solids have certain _surface_ properties and certain properties that surfaces do _not_ have; and suppose we say the _surface_ properties of solids are _natural_ but the other properties are so mysterious that they must be “_super_natural” or somehow “divine”; and suppose we then say that solids are unions, mixtures, compounds or hybrids of surfaces and something divine or _super_natural; is it not evident that, if we did that, we should be again blundering like fools? Type-confusing fools? Dimension-mixing fools? That such would be the case any one can see. Let us now consider animals and human beings, and let us look squarely and candidly at the facts. To get a start, think for a moment of plants. Plants are living things; they take, transform and appropriate the energies of sun, soil, and air, but they have _not_ the _autonomous_ power to move about in space; we may say that plants constitute the lowest order or class or type or dimension of life—the dimension _one_; plants, we see are binders of the _basic_ energies of the world. What of animals? Like the plants, animals, too, take in, transform and appropriate the energies of sun, soil and air, though in large part they take them in forms already prepared by the plants themselves; but, _unlike_ the plants, animals possess the _autonomous_ power to move about in space—to creep or crawl or run or swim or fly—it is thus evident that, compared with plants, animals belong to a higher order, or higher class, or higher type, or higher dimension of life; we may therefore say that the type of animal life is a type of _two_ dimensions—a two-dimensional type; I have called them space-binders because they are distinguished, or marked, by their autonomous power to move about in space, to abandon one place and occupy another and so to appropriate the natural fruits of many localities; the life of animals is thus a life-in-space in a sense evidently not applicable to plants. And now what shall we say of _Man_? Like the animals, human beings have indeed the power of mobility—the autonomous power to move—the capacity for binding space, and it is obvious that, if they possessed no capacity of higher order, men, women and children would indeed be animals. But what are the facts? The facts, if we will but note them and reflect upon them, are such as to show us that the chasm separating human nature from animal nature is even wider and deeper than the chasm between animal life and the life of plants. For man improves, animals do not; man progresses, animals do not; man invents more and more complicated tools, animals do not; man is a creator of material