Thomas Malthus (1766-1834) published his theory of population ("An essay on the principle of population") in 1798. In it he laid out the argument that there existed in the world a constant pressure towards population growth which was counteracted throughout history by "positive checks" that included "war, famine, and disease". He argued that food shortages, in particular, were inevitable as population grew because population could grow geometrically (build upon itself: 2,4,8,16...) whereas food production could grow only arithmetically (2,3,4,5...). Hence, according to this "Malthusian Equation", population would soon outstrip available food. A rise in population would soon be checked by a rise in the death rate. Malthus was a clergyman in the Church of England, and ultimately he argued that this balance was part of the Divine Order of the world (see excerpts). One consequence of this was that the Church of England opposed birth control up until the 1930s.

Much of his argument was directed at the relative growth of different classes within the population of England. Those who did not practice "preventative checks" on their family size would soon outstrip their means and so fall in status. For Malthus the only acceptable preventative check was delaying marriage until one was financially able to support a family. Birth control, inside or outside of marriage, he viewed as a "vice" (an "improper art") that threatened the moral order of society. Ultimately, in his view, poverty existed because of growth in family size caused by a lack of self restraint, and the poor, as a class, had entirely themselves to blame for their situation. Therefore he opposed "Poor Laws" that would provide support to the poor on the grounds that such support would only reinforce their lack of restraint at the expense of others in society. Such laws would undermine the fabric of society (see excerpts).

In the world today one hears various echoes of Malthus: First, in the view that ultimately population growth is the cause of poverty, famine and environmental degradation; second, in the arguments of Garrett Hardin regarding the "Tragedy of the Commons"; and third, in the "welfare" debate in the United States in which some argue that welfare is the cause of single parenthood.  Such views are termed "Neo-Malthusian".

Incidentally, Malthus was by no means the first to think in "Malthusian" terms:
"What most frequently meets our view (and occasions complaint), is our teeming population: our numbers are burdensome to the world,
[The earth] scarcely can provide for our needs; as our demands grow greater, our complaints against nature's inadequacy are heard by all. The scourges of pestilence, famine, wars, and earthquakes have come to be regarded as a blessing to overcrowded nations, since they serve to prune away the luxuriant growth of the human race."
spacer graphicTertullian (c. 155-220)
De anima