The difficulty of over-population was conspicuous in the minds of
Aristotle and Plato, and these philosophers both held that the State had
a right and a duty to control it.

But some States were almost annihilated because they were not
sufficiently populous, and Aristotle attributes the defeat of Sparta on
one celebrated occasion to this fact. He says:--"The legislators wanting
to have as many Spartans as they could, encouraged the citizens to have
large families, and there is a law at Sparta, that the father of three
sons should be exempt from military service, and he who has four, from
all the burdens of the State. Yet it is obvious that if there were many
children, the land being distributed as it is, many of these must
necessarily fall into poverty."

The problem in the mind of the Greek philosophers was this.
Over-population is a cause of poverty; under-population is a cause of
weakness. Defectives are an additional burden to the State. How shall
population be so regulated as to established an equilibrium between the
stability of the State, and the highest well-being of the citizens?

The combined philosophy of the Greeks counselled the encouragement of
the best citizens to increase their kind, and the practice of the
exposure of infants and abortion.

A century of debate has raged round the name of Malthus, the great
modern analyst of the population problem. He published his first essay
on population in 1798, a modest pamphlet, which fed so voraciously on
the criticism supplied to it, that it developed into a mighty
contribution to a great social problem, second only in time and in