Malthusian theory, it has seemed in the minds of political economists a self-evident truth. These two theories mutually blend with, strengthen, and defend each other, while they both derive additional support from a principle brought prominently forward in the discussions of the theory of rent—viz., that past a certain point the application of capital and labor to land yields a diminishing return. Together they give such an explanation of the phenomena presented in a highly organized and advancing society as seems to fit all the facts, and which has thus prevented closer investigation.
Which of these two theories is entitled to historical precedence it is hard to say. The theory of population was not formulated in such a way as to give it the standing of a scientific dogma until after that had been done for the theory of wages. But they naturally spring up and grow with each other, and were both held in a form more or less crude long prior to any attempt to construct a system of political economy. It is evident, from several passages, that though he never fully developed it, the Malthusian theory was in rudimentary form present in the mind of Adam Smith, and to this, it seems to me, must be largely due the misdirection which on the subject of wages his speculations took. But, however this may be, so closely are the two theories connected, so completely do they complement each other, that Buckle, reviewing the history of the development of political economy in his "Examination of the Scotch Intellect during the Eighteenth Century," attributes mainly to Malthus the honor of "decisively proving" the current theory of wages by advancing the current theory of the pressure of population upon subsistence. He says in his "History of Civilization in England," Vol. 3, Chap. 5:
