For a more specific illustration of the nature of a problem we may examine the problem of population in its simplest form. When Malthus first stated it he assumed, for the purposes of argument, two elements evolving at different rates. Population, he said, doubled every twenty-five years; the produce of land could be increased in the same time by an amount “equal to what it at present produces.”[18] He was writing about the year 1800. The population of England he estimated at seven millions, and the food supply as adequate to that number. There was then, in 1800, no problem. By 1825 the population, according to his estimate of its rate of increase, would have doubled, but the food supply would also have doubled. There would be no problem of population. But by 1850 the population would stand at twenty-eight millions; the food supply would have increased only by an amount to support an additional seven millions. The problem of excess population, or, if you like, of food scarcity, would have appeared. For while in 1800 and in 1825 the food available for each person would be the same, in 1850, owing to the uneven rate of growth, there would be only a three-quarter ration for each person. And this altered relationship Malthus rightly called a problem. Suppose, now, we complicate Malthus’s argument a bit by assuming that in 1850 people had learned to eat less and felt more fit on the three-quarter ration. There would then be no problem in 1850, for the adjustment of the two variables—food and people—would be satisfactory. Or, on the contrary, suppose that soon after 1800 people had demanded a higher standard of living and expected more food, though the necessary additional food was not produced. These new demands would create a problem. Or suppose, as was actually the case,[19] the food supply increased faster than Malthus had assumed it could, though population did not. The problem of population would not arise at the date he predicted. Or suppose the increase of population was reduced by birth control. The problem, as Malthus first stated it, would not arise.[20] Or suppose the food supply increased faster than the population could consume it. There would then be a problem not of population but of agricultural surplus. In an absolutely static society there would be no problems. A problem is the result of change. But not of the change in any self-contained element. Change would be unnoticeable unless we could measure it against some other element which did not change at the same pace. If everything in the universe expanded at a mile a minute, or shrank at the same rate, we should never know it. For all we can tell we may be the size of a mosquito one moment in the sight of God, and of an elephant the next; we cannot tell if mosquitoes and elephants and chairs and planets change in proportion. Change is significant only in relation to something else.