Land, labor, and capital are the three factors of production. If we remember that capital is thus a term used in contradistinction to land and labor, we at once see that nothing properly included under either one of these terms can be properly classed as capital. The term land necessarily includes, not merely the surface of the earth as distinguished from the water and the air, but the whole material universe outside of man himself, for it is only by having access to land, from which his very body is drawn, that man can come in contact with or use nature. The term land embraces, in short, all natural materials, forces, and opportunities, and, therefore, nothing that is freely supplied by nature can be properly classed as capital. A fertile field, a rich vein of ore, a falling stream which supplies power, may give to the possessor advantages equivalent to the possession of capital, but to class such things as capital would be to put an end to the distinction between land and capital, and, so far as they relate to each other, to make the two terms meaningless. The term labor, in like manner, includes all human exertion, and hence human powers whether natural or acquired can never properly be classed as capital. In common parlance we often speak of a man’s knowledge, skill, or industry as constituting his capital; but this is evidently a metaphorical use of language that must be eschewed in reasoning that aims at exactness. Superiority in such qualities may augment the income of an individual just as capital would, and an increase in the knowledge, skill, or industry of a community may have the same effect in increasing its production as would an increase of capital; but this effect is due to the increased power of labor and not to capital. Increased velocity may give to the impact of a cannon ball the same effect as increased weight, yet, nevertheless, weight is one thing and velocity another. Thus we must exclude from the category of capital everything that may be included either as land or labor. Doing so, there remain only things which are neither land nor labor, but which have resulted from the union of these two original factors of production. Nothing can be properly capital that does not consist of these—that is to say, nothing can be capital that is not wealth. But it is from ambiguities in the use of this inclusive term wealth that many of the ambiguities which beset the term capital are derived.