honour to the work of his great predecessor in economic studies, Adam
Smith.

Malthus's first essay defined and described the laws of multiplication
as they apply only to the lower animals and savage man. It was only in
his revised work, published five years later, that he described moral
restraint as a third check to population.

Adverse criticism had been bitter and severe, and Malthus saw that his
first work had been premature. He went to the continent to study the
problem from personal observation in different countries. He profited by
his observation, and by the writings of his critics, and published his
matured work in 1803.

The distinguishing feature about this edition was the addition of moral
restraint as a check, to the two already described, vice and misery.

Malthus maintained that population has the power of doubling itself
every 25 years. Not that it _does_ so, or _had done_ so, or _will do
so_, but that it is _capable_ of doing so, and he instanced the American
Colonies to prove this statement.

One would scarcely think it was necessary to enforce this distinction,
between what population has done, or is doing, and what it is capable
of doing. But when social writers, like Francesco Nitti (Population and
the Social System, p. 90), urge as an argument against Malthus's
position that, if his principles were true, a population of 176,000,000
in the year 1800 would have required a population of only one in the
time of our Saviour, it is necessary to insist upon the difference
between _increase_ and the _power of increase_.