Chapter XXVI: Section 1: The Theory of Thomas Doubleday Revived

In 1837 Thomas Doubleday [51] maintained that the rising birth-rate of his own time was closely connected with the fall in the standard of living, and his argument implied that, in order to check the excessive birth-rate, it was necessary to improve the condition of the mass of the people. Four years later he published _The True Law of Population_, wherein he stated that when the existence of a species is endangered--

"A corresponding effort is invariably made by Nature for its
preservation and continuance by an increase of fertility, and that this
especially takes place whenever such danger arises from a diminution of
proper nourishment or food, so that consequently the state of depletion
or the deplethoric state is favourable to fertility, and that, on the
other hand, the plethoric state, or state of repletion, is unfavourable
to fertility in the ratio of the intensity of each state."

By a series of experiments on plants Doubleday discovered that "whatever might be the principle of manure, _an overdose_ of it invariably induced sterility in the plant." Although his formula is deficient in that food is selected as the one factor in environment which influences fertility, and although it may be an overstatement to claim that fertility varies in exact proportion to abundance or to scarcity, nevertheless his formula contains an important truth which literally knocks the bottom out of the whole Malthusian case.

It is a sad reflection that, while the falsehoods of Malthus have been blindly accepted for the greater part of a century, the work of Doubleday was almost lost in oblivion. His shade has now been recalled to the full centre of the stage, and for this the credit is due to Mr. C.E. Pell. His recent book [52] is a stimulating essay on the declining birth-rate, and contains much evidence that supports the main contention of Doubleday. Although it is impossible to agree with all the deductions made by Mr. Pell, he has nevertheless done a public service by restating the problem of the birth-rate in a new way, by effectively bursting the Malthusian bubble, and by tabulating fresh evidence against the birth-controllers.