But the products of the earth increase only in an arithmetical progression, and in fifty years the food supply would be too small for the demand.

Thus the oscillation between numbers and food supply would recur, and the happiness of the species would come to an end.
Godwin and his adherents could reply that one of the checks on over-population is prudential restraint, which Malthus himself recognised, and that this would come more extensively into operation with that progress of enlightenment which their theory assumed.
[Footnote: This is urged by Hazlitt in his criticism of Malthus in the Spirit of the Age.] But the criticisms of Malthus dealt a trenchant blow to the doctrine that human reason, acting through legislation and government, has a virtually indefinite power of modifying the condition of society.

The difficulty, which he stated so vividly and definitely, was well calculated to discredit the doctrine, and to suggest that the development of society could be modified by the conscious efforts of man only within restricted limits.

[Footnote: The recent conclusions of Mr.
Knibbs, statistician to the Commonwealth of Australia, in vol.i.

of his Appendix to the Census of the Commonwealth, have an interest in this connection.