to
the high intellectual attainments of her people, and that the rapidly
decreasing birth-rate is due to a rapid increase of her intellectual
power during recent years.

Ireland and New Zealand would be equally pleased could they believe that
their low, and still decreasing birth-rate is due to the lessening of
the sexual instinct, attendant upon, and resulting from a high and
increasing intellectual power and activity.

The fact is, that the sexual instinct is so immeasurably in excess of
the maximum power of procreation in the female, that an enormous
reduction in sexual power would require to take place before it would
have any effect on the number of children born.

The number of children born is controlled by the capacity of the human
female to bear children, and one birth in every two years during the
child-bearing period of life is about the maximum capacity.

A moderate diminution in the force of the sexual instinct might lead to
a decrease in the marriage rate, but it would require a very serious
diminution bordering on total extinction of the instinct to exert any
serious effect on the fecundity of marriage.

All that can be claimed for this theory of population is, that,
reasoning from known physiological analogies, we might expect a
weakening of the desire for marriage, coincident with the general
development of intellect in the race.

There are as yet no facts to prove that such weakening has taken or is
taking place, nor are there facts to prove that population has in any
way suffered from this cause.

If such a law obtained, and resulted in a diminished birth-rate, the
future of the race would be the gloomiest possible. An inexorable law
would determine that there could be no mental evolution, for the best of
the race would cease to propagate their kind. All who would arrive at
this standard of mental growth would become barren. And against this
there could be no remedy.

One of the main contentions of this work is that the best have to a
large extent ceased to propagate their kind, but it is not maintained
that this is the result of a biological law, over which there is no
control. It can be safely claimed that to Malthus's three checks to
population--vice, misery, and moral restraint, the demographic phenomena
of a century have added no other. The third check, however, moral
restraint, must be held to include all restraint voluntarily placed by
men and women on the free and natural exercise o