From this reasoning I infer, that no exact judgment can be formed, as to the numbers in any society, from the single datum of the annual number of deaths among them; and although the just proportion between numbers and deaths may exactly be determined in one particular place, yet that proportion will not serve as a general standard, and being taken for granted may lead to error.
Were no body to marry but such as could maintain their children, the bills of births and burials would, I apprehend, diminish, and yet numbers might remain as before; and were every body to marry who could procreate, they certainly would increase, but still numbers would never exceed the proportion of subsistence. Could we but see bills of births and deaths for the city of Rome, while in all its glory; or indeed for the sugar colonies in America, where slaves are imported, adding the number of those imported to that of births, and supposing the colony neither upon the growing nor the declining hand, then the deaths and births would be equal; but the proportion of them to all in the colony, I apprehend, would be far less than in any state in Europe, where slavery does not prevail.
It may be alledged, that were all to marry, the consequence would be a great multiplication. I say not; or if it were, what sort of multiplication would it be? A multitude of children who never could come to manhood; or who would starve their parents, and increase misery beyond expression. All therefore that can be learned from bills of mortality, &c. is, that if the births exceed the deaths, and that all remain in the country, numbers will increase; that if the deaths exceed the births, numbers will diminish; but while they stand at par, no conclusion can be drawn as to numbers in general: these will be in a less proportion as abusive procreation goes forward; and, _vice versa_, they will be in a greater. There still hangs a cloud upon this subject: let me therefore reason upon an example. Suppose the inhabitants of a country to stand at 6,000,000, one thirtieth to die every year, and as many to be born, that is, the births and burials to stand at 200,000; that every three marriages subsisting produce a child every year, that is 600,000 marriages; let the quantity of food be supposed the same, without a possibility of being augmented. Would not the consequence be, that numbers could not increase? Now let me suppose marriages carried to 1,000,000, I say the effect would be, either that they would become in general less fruitful, or if they suffered no diminution in this particular, that the bills of births and deaths would rise to 333,333; that is to say, they would be to the number of inhabitants as 1 to 18, instead of being as 1 to 30. Now this increase of mortality proceeding from want of food, either the old would starve the young, or the young would starve the old; or a third case, more probable than either, would happen, the rich would starve the poor. What would be the consequences in all these three suppositions? In the first, the number of 6,000,000 would be found to diminish; because the proportion of large consumers would rise, and mortality would increase among the children. In the second, the standard number would augment, because the proportion of small consumers would rise, and mortality would increase among the parents. In the third, numbers would remain pretty much the same, but misery and distress would lay all the lower classes waste. It is computed that one half of mankind die before the age of puberty in countries where numbers do not augment; from this I conclude, that too many are born. If methods therefore are fallen upon to render certain diseases less mortal to children, all the good that will be got by it, in general, will be to render old people of the lower classes more wretched; for if the first are brought to live, the last must die.