progress from infancy to old age; yet, as it must still be uncertain whether at present it be advancing to its point of perfection or declining from it, we cannot thence presuppose any decay in human nature.39 To prove, therefore, or account for the greater populousness of antiquity by the imaginary youth or vigour of the world will scarcely be admitted by any just reasoner; these general physical causes ought entirely to be excluded from that question.
There are indeed some more particular physical causes of great importance. Diseases are mentioned in antiquity which are almost unknown to modern medicine, and new diseases have arisen and propagated themselves of which there are no traces in ancient history. And in this particular we may observe, upon comparison, that the disadvantage is very much on the side of the moderns. Not to mention some others of less importance, the smallpox commits such ravages as would almost alone account for the great superiority ascribed to ancient times. The tenth or the twelfth part of mankind destroyed every generation should make a vast difference, it may be thought, in the numbers of the people; and when joined to venereal distempers, a new plague diffused everywhere, this disease is perhaps equivalent, by its constant operation, to the three great scourges of mankind—war, pestilence, and famine. Were it certain, therefore, that ancient times were more populous than the present, and could no moral causes be assigned for so great a change, these physical causes alone, in the opinion of many, would be sufficient to give us satisfaction on that head. {p109}
But is it certain that antiquity was so much more populous as is pretended? The extravagancies of Vossius with regard to this subject are well known; but an author of much greater genius and discernment has ventured to affirm that, according to the best computations which these subjects will admit of, there are not now on the face of the earth the fiftieth part of mankind which existed in the time of Julius Cæsar. It may easily be observed that the comparisons in this case must be very