The great philosophers of Greece, such as Plato and Aristotle, are the origin of all real civilisation in succeeding ages throughout Europe: and have saved us from the deluge of crude theologies, such as those of Palestine or less cultured tribes. The so-called divine law of “Increase and multiply and replenish the earth,” and other equally vague and meaningless exclamations, are in strongest contrast with the scientific reasoning of these _masters of all the learned_. Plato, in his “Republic,” limits the number of free citizens in his ideal state to five thousand and forty. Procreation, he maintains, when it proceeds too fast, may be checked, or when it goes on too slowly, may be encouraged, by the proper distribution of honors and marks of ignominy, and by the admonitions of the elders to prevent or promote it according to circumstances. Mr. John Stuart Mill evidently was of a similar opinion, and his followers have advocated State intervention as a cure for poverty. Plato also anticipated Mr. Darwin himself and the modern Darwinians, who lay such great and just stress on the point of the rational selection of parents. In the fifth book of his “Republic,” he proposes that the most healthy men should be joined in marriage to the finest specimens among the women, and the inferior citizens should be paired with each other. He next proposes that the children of the first class alone shall be brought up, the others not. It will doubtless be one of the results of the Neo-Malthusian movement of this day, that persons afflicted with hereditary disease will not so often desire to become parents as the healthy, whilst they may follow the advice of Professor Mantegazza, of Florence, and “marry, but not procreate.” From these and other passages it is clear that Plato well saw the tendency of population to increase beyond the means of subsistence. His expedients for checking it were not permissible, indeed, but the extent to which they were to be used shows how great he perceived the difficulty to be. How backward most modern nations are in speculation on such points may be judged of by the unwillingness in Germany, England, and even in France to look the question fairly in the face. In Plato’s time wars were nearly perpetual, and very destructive, and if, whilst knowing this, he could still contemplate the destruction of the children of the poorer and sicklier of the population, of all who were born when their parents were either too young or too old, the fixing of the date of marriage late, and the regulating the number of marriages, his reasonings and experience must have pointed out to him the terrible tendency of population to over-pass the means of subsistence.