but of all the seas and oceans of the world, so the limit of subsistence in any particular place is not the physical limit of that place, but the physical limit of the globe. Fifty square miles of soil will in the present state of the productive arts yield subsistence for only some thousands of people, but on the fifty square miles which comprise the city of London some three and a half millions of people are maintained, and subsistence increases as population increases. So far as the limit of subsistence is concerned, London may grow to a population of a hundred millions, or five hundred millions, or a thousand millions, for she draws for subsistence upon the whole globe, and the limit which subsistence sets to her growth in population is the limit of the globe to furnish food for its inhabitants.
But here will arise another idea from which the Malthusian theory derives great support—that of the diminishing productiveness of land. As conclusively proving the law of diminishing productiveness it is said in the current treatises that were it not true that beyond a certain point land yields less and less to additional applications of labor and capital, increasing population would not cause any extension of cultivation, but that all the increased supplies needed could and would be raised without taking into cultivation any fresh ground. Assent to this seems to involve assent to the doctrine that the difficulty of obtaining subsistence must increase with increasing population.
But I think the necessity is only in seeming. If the proposition be analyzed it will be seen to belong to a class that depend for validity upon an implied or suggested qualification—a truth relatively, which taken absolutely becomes a non-truth. For that man cannot exhaust or lessen the powers of nature follows from the indestructibility of matter and the persistence of force. Production and consumption are only relative terms. Speaking absolutely, man neither produces nor consumes. The whole human race, were they to labor to infinity, could not make this rolling sphere one atom heavier or one atom lighter,
