Self-un-fulfilling prophecies

Thomas Malthus is famous for predicting that population growth, which grows geometrically, will eventually outstrip the arithmetic growth in our ability to grow food (or provide any important resource such as energy). Poor guy, he's always been proven wrong (at least so far).

Of course, Malthus ultimately has to be right. For a ridiculous example that proves the point, I think it's pretty clear that the Earth alone cannot support more than, say, 10 to the 25 (1 followed by 25 zeros) people because the people alone would then weigh more than the whole weight of the earth.

But this is indeed a ridiculous limit; the more salient point in the criticism of Malthus has generally been the accurate observation that he neglected to account for the effects of innovation, and indeed innovation has always intervened before Malthusian limits could apply.

A great example of this is the very food production which spurred his theories, where the capacity of 19th century agriculture extrapolated across all potentially arable land would be sufficient to feed perhaps a billion or 2 people. But alas here we are today pushing 7 billion people, with lots of wasted food and an obesity problem in many nations. This is due to innovations in fertilizers and pesticides, which have dramatically increased yields faster than the population has grown.

Yet there is a perverse self-unfulfilling prophecy at work here: human innovation is motivated, at least in part, by the fear that failure to innovate will prove Malthus right. As described in the book "The Alchemy of Air," it was precisely the fear of starving populations that drove the discoveries of new fertilizers.

So I think there is an interesting irony that it is precisely the fear of Malthus being right which has led to his consistently being proven wrong.