[bryanlarsen]

Malthus's arguments may have made some sense when he made them, the green revolution may have been difficult to predict back then. But any neo-Malthusian arguments don't pass the smell test today.

1) If we were running out of food it would be reflected in the price. The price of wheat in British pounds has stayed relatively constant for ~800 years, staying within the range of 1-5 pounds per bushel. That's right, we've had inflation in everything but the price of food.

A bushel of wheat contains approximately one month's worth of calories. You used to be able to buy a slave for ~100 pounds. Today that buys about a day's worth of labour, but it still buys the same amount of wheat.

2) It's trivially easy to grow more food per acre than today's farms do. There are probably hundreds of different ways we could do so. We don't do any of them because they are all too expensive. If the price of food rose, those techniques would become viable. For example, we can increase production several orders of magnitude in temperate regions by building greenhouses.

We had a food price spike 5 years ago, the price of wheat went to about $10/bushel, a historically unprecedented level. Farmers responded by farming more intensively, and now the price is below $4/bushel.

3) To a first order approximation, food is created from energy and water. We use raw solar energy for food production because it's the cheapest, but we're reaching a point where it's starting to become feasible to use other forms of energy. Given desalination, our water supply is also only limited by our energy supply. Virtually all of the other secondary inputs to food production are basically transformed energy: diesel, fertilizer, herbicides, et cetera.

And every other element required for food production usually has its prevalence expressed as a percentage of the earth's crust. For example, Potassium is 2.6% of the earth's crust. So for all intents and purposes, unlimited. The energy required to extract the potassium is the limiting factor, not the potassium itself.

Is our world energy supply finite? Yes, but we can expand it using nuclear & solar faster than we can expand the world's population.

[danbruc]

If you increased our energy consumption by 1 % per year, we would all be dead in less than 1000 years because at that point the surface temperature of the Earth would have reached the boiling point of water.

EDIT: In case the down votes are for the numbers. The total emission of an ideal black body with surface area of 510.1 million km² at 373.15 K is 560,791 TW. The world total primary energy supply in 2012 is estimated to have been 155,505 TWh which is 17.75 TW on average. That is a factor of 31,591 from what Earth could radiate into space at 100 °C or 1,041 years of 1 % growth per year.

[TheCoelacanth]

If we increased our energy production to 20000 times our current production (roughly 1000 years at 1% growth), I highly doubt we would still be stuck on Earth.

[danbruc]

Leaving Earth does not really help that much - the number of stars and planets you can reach only increases with the third power - assuming an homogeneous distribution - and after some time more like with the second power due to the flat shape of the Milky Way and is in consequence quickly overwhelmed by exponential growth. You would not really get that far from Earth before you would already have to consume all the resources of the galaxy assuming some constant rate of growth on the order of 1 % per year.