Today is the anniversary of the birth of Thomas Malthus. Many people hesitate to recognize Malthus, dismissing his essay on population as faulty. For those of you unfamiliar with his essay posited that unchecked population growth always exceeds the growth of the means of subsistence. The problem with his hypothesis was it failed to take changing levels of capital into account. Since he wrote at the beginning of the Industrial Revolution, he was soon proved wrong.
But he also wrote on rent and Say's Law. Regarding rent, Malthus argued against the idea of rent being a cost of production, rather believing that it was a deduction from surplus. Regarding Say's Law, Malthus felt that general gluts were possible, thus negating the "supply creates its own demand" idea that felt those periods of overproduction weren't possible. You find some good bios on Malthus here, here and here.