A great deal of criticism has been directed against the Malthusian theory on the ground that it advocated the practice of vice as a restraint upon the tendency of population to increase more rapidly than food supply. Such criticism is without just foundation. Malthus did not advocate vice for the purpose of restricting population. But he recognized that vice does, as a matter of fact, tend to restrict population.

There are, however, three principal lines of criticism which may justly be urged against Malthus. First, he underestimates the possibilities of increased food supply. There is no ground for making the general assertion that as population increases from two to four, food supply can increase only from two to three. Under the operation of the law of diminishing returns and without changing the area of land cultivated by the given population or changing its methods of cultivation, while the labor supply increases from two to four the product could not increase from two to four, but it might well increase more than from two to three. But Europe during the past century has increased the area from which it draws its food supply and now depends in ever-increasing measure upon the Americas and Australia for subsistence. Moreover, the methods of cultivation of the soil have improved marvelously within the last century. The population of England and Wales increased in the century following the publication of Malthus' essay from nine millions to thirty-two and a half millions, and this increase in population took place in the presence of an increasing standard of living.

Second, there are other checks upon increase of population besides vice, misery, and moral restraint as defined by Malthus. The desire of parents to keep their daughters with them as long as possible serves in some cases to defer marriages. So, too, do customs which demand that the parents furnish a dowry. The feminist movement, the modern tendency to keep children longer in school, and compulsory military service, all act in the same direction. Many other checks might be enumerated which do not fall under Malthus' classification of vice, misery, and moral restraint.

3. Third, along with increase in numbers there is growth in national military and political strength. This sometimes makes it possible for a country to exploit its weaker neighbors in an economic sense, or to resist economic exploitation on the part of stronger neighbors. To this extent an increase in population tends to improve the food supply.