thing in the mind of Malthus.

But this is not so.

A physiological law makes it possible, in a large proportion of strictly
normal women, for union to take place without fertilisation. If it were
possible to maintain an intermittent restraint in strict conformity with
this law, it would control considerably the population of the world.

It is easier to practice intermittent than to practice constant
restraint.

It is just here that Malthus failed to anticipate the future. Malthus
believed that "moral restraint" would lessen the marriage rate, but
would have no direct effect on the fecundity of marriage.

A man would not put upon himself the self-denial and restraint, which
abstinence from marriage implied, for a longer period than he could
help.

The greater the national prosperity, therefore, the higher the
birth-rate. But prosperity keeps well in advance of the birth-rate; in
other words, population, though it still _tends_ to, does not actually
_press_ upon the food supply.

If the moral restraint of Malthus be extended so as to include
intermittent moral restraint within the marriage bond, then, under one
or other, or all of his three checks, vice, misery, and moral restraint,
will be found the explanation of the remarkable demographic phenomena of
recent years.