In short, the Roman habits had become “unfavourable to industry, and therefore to population.” The very necessity for such a law as the Papia Poppæa would indicate a moral depravity inconsistent with habits of industry. This strong argument had escaped even Hume, who thought that the people would increase very fast under the Peace of Trajan and the Antonines, forgetting that the people could not unlearn their habits in so short a time; unlearning is harder than learning, especially for a whole people; and, “if wars do not depopulate much when industry is in vigour, peace does not increase population much when industry is languishing.”[226] Contrariwise, it might be argued that the prevention of child-murder in India will not cause over-population, when it is part of a general policy accustoming the people to European habits. Allow, then, that general viciousness is inconsistent with general industry, and it follows that those ancient nations in which the first prevailed were less populous than the modern. This seems to be the argument of Malthus brought to a focus. From the absence of censuses,[227] it is strictly deductive; there _could_ not have been so many people as now, and therefore there _were_ not.[228] Expressed in more technical language, the meaning is, that where there is nothing present but the positive check and the lower kind of preventive, the habits of the people are necessarily such as to hinder an increase of food and thereby of population. When Europe was less civilized, it was not more, but less thickly peopled.[229] This argument seems to be weakened by one consideration—that the poor in our day put more into their idea of necessaries; they have a higher standard of living than the poor 2000 years ago. It might therefore be said with justice that over-population (a peopling beyond the food) begins much sooner with us than with them, for it begins at a point much farther removed from starvation, and that therefore with the ancients a given amount of food would go farther and feed more. But, if we look only to the poor in each case, the difference between the ancient standard of comfort and the modern is unhappily much smaller than the difference between their meagre industrial resources and our ample ones, for our powers of production have grown far more rapidly than the comfort of our labouring population. Such difference as there is in the standards is only made possible by moral restraint, which has a closer affinity with modern civilization than with ancient or mediæval.[230] The history of modern civilization is largely the history of the gradual victory of the third check over the two others; and, as one of the chief allies of the third has been commercial ambition, the victory of moral restraint, by causing a larger industry, has caused in the end not a smaller, but a larger population.[231] The increase by being deferred has been made only the more certain and permanent.