CHAP. III.
Upon what Principles, and from what natural Causes do Mankind multiply? And what are the effects of Procreation in Countries where Numbers are not found to increase?
The multiplication of mankind has been treated of in different ways; some have made out tables to shew the progression of multiplications, others have treated the question historically. The state of numbers in different ages of the world, or in different countries at different times, has been made the object of inquiry; and the most exact scrutiny into antient authors, the means of investigating the truth of this matter. All passages relative to the subject have been laid together, and accompanied with glosses and interpretations the most plausible, in order to determine the main question. The elaborate performances of Mr. Hume, and Mr. Wallace, who have adopted opposite opinions in regard to the populousness of the antient world, have left nothing new to be said upon this subject; at least the application they appear to have given in examining the antients, is a great discouragement to any one who might otherwise still flatter himself, there, to find out circumstances proper to cast a new light upon the question.
My intention in this chapter is not to decide, nor even to give my opinion upon that matter, far less to combat the arguments advanced on either side. I am to consider the question under a different point of view; not to enquire what numbers of people were found upon the earth at a certain time, but to examine the natural and rational causes of multiplication. If we can discover these, we may perhaps be led to judge how far they might have operated in different ages and in different countries.
The fundamental principle of the multiplication of all animals, and consequently of man, is generation; the next is food: generation gives existence, food preserves it. Did the earth produce of itself the proper nourishment for man, with unlimited abundance, we should find no occasion to labour in order to procure it. Now in all countries found inhabited, as in those which have been found desolate, if the state of animals be inquired into, the number of them will be found in proportion to the quantity of food produced by the earth, regularly throughout the year, for their subsistence. I say, regularly throughout the year, because we perceive in those animals which produce in great abundance, such as all the feathered genus, that vast multitudes are destroyed in winter; they are brought forth with the fruits of the earth, and fall in proportion. This principle is so natural, that I think it can hardly be controverted.
As to man, the earth does not spontaneously produce nourishment for him in any considerable degree. I allow that as some species of animals support life by devouring others, so may man; but it must be observed, that the species feeding must always be much inferior in number to the species fed upon. This is evident in reason and in fact.
Were the earth therefore uncultivated, the numbers of mankind would not exceed the proportion of the spontaneous fruits which she offers for their immediate use, or for that of the animals which might be the proper nourishment of man.
There is therefore a certain number of mankind which the earth would be able to maintain without any labour: allow me to call this quantity (A). Does it not, from this exposition of the matter, appear plain, that without labour (A) never can increase any more than animals, which do not work for themselves, can increase beyond the proportion of food provided for them by nature? Let it be however observed, that I do not pretend to limit (A) to a determined number. The seasons will no doubt influence the numbers of mankind, as we see they influence the plenty of other animals; but I say (A) will never increase beyond the fixed proportion above-mentioned.
Having resolved one question with regard to multiplication, and shewn that numbers must become greater or smaller according to the productions of nature, I come to the second thing proposed to be treated of in the chapter: to wit, what will become of the generative faculty after it has produced the full proportion of (A), and what effects will afterwards follow.
We see how beneficent, I might have said prodigal, nature is, in bestowing life by generation. Several kinds of animals, especially insects, multiply by thousands, and yet the species does not appear annually to increase. No body can pretend that particular individuals of any species have a privilege to live, and that others die from a difference in their nature. It is therefore reasonable to conclude, that what destroys such vast quantities of those produced, must be, among other causes, the want of food. Let us apply this to man.