Who is Malthus?

I am going to pre-emptively answer this question which will inevitably be asked by anyone who reads or sees Urinetown, The Musical.

Thomas Robert Malthus, England's first academic economist, is most famous for his Essay on the Principle of Population (1798, expanded in 1803), which the bio linked above summarizes as follows:

In this famous work, Malthus posited his hypothesis that (unchecked) population growth always exceeds the growth of means of subsistence.  Actual (checked) population growth is kept in line with food supply growth by "positive checks" (starvation, disease and the like, elevating the death rate) and "preventive checks" (i.e. postponement of marriage, etc. that keep down the birthrate), both of which are characterized by "misery and vice".  Malthus's hypothesis implied that actual population always has a tendency to push above the food supply.  Because of this tendency, any attempt to ameliorate the condition of the lower classes by increasing their incomes or improving agricultural productivity would be fruitless, as the extra means of subsistence would be completely absorbed by an induced boost in population.  As long as this tendency remains, Malthus argued, the "perfectibility" of society will always be out of reach.