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, could not add to or diminish by one iota the sum of the forces whose everlasting circling produces all motion and sustains all life. As the water that we take from the ocean must again return to the ocean, so the food we take from the reservoirs of nature is, from the moment we take it, on its way back to those reservoirs. What we draw from a limited extent of land may temporarily reduce the productiveness of that land, because the return may be to other land, or may be divided between that land and other land, or perhaps, all land; but this possibility lessens with increasing area, and ceases when the whole globe is considered. —Progress & Poverty — Book II, Chapter 3: Population and Subsistence: Inferences from Analogy
read the corresponding section in Bob Drake's abridgement ...
But another idea arises that gives Malthus great support: the diminishing productiveness of land. Beyond a certain point, so the argument goes, land yields less and less to additional labor and capital. Otherwise, a growing population would not extend cultivation to additional land. Acknowledging this appears to involve accepting the doctrine that a growing population increases the difficulty of obtaining subsistence.
But if we analyze this proposition, we see that it depends on an implied qualification. It is true in a relative context, but not when taken absolutely. Production and consumption are only relative terms. Speaking absolutely, people neither produce nor consume. They cannot exhaust or lessen the powers of nature. If the whole human race were to work forever, they could not make the Earth one atom heavier or lighter. Nor could they augment or diminish the forces that produce all motion and sustain all life.*
Water taken from the ocean must eventually return to the ocean. So too, the food we take from nature is, from the moment we take it, on its way back to those same reservoirs. What we draw from a limited extent of land may temporarily reduce the productiveness of that land. But the return will go to other land.
Life does not use up the forces that maintain life. We come into the material universe bringing nothing; we take nothing away when we depart. The human being, in physical terms, is just a transitory form of matter, a changing mode of motion.