The earth is subject, like the other planets, to the laws of motion; it suffers within itself a continual strife among its elements; the sea and the land seem to be forever at war; each moment produces new combinations.
Men, in an abode so subject to change, are likewise in an unsettled condition: a hundred thousand causes may operate against them capable of destroying them, and much more of increasing or diminishing their number.
I do not refer to those special catastrophes, so common in history, which have destroyed whole cities and kingdoms: there are general ones which many a time have brought the human race next door to destruction.
History is full of those universal plagues which have one after the other desolated the earth. They tell of one which was so violent that it blasted the very roots of plants, and made itself felt throughout the known world, as far as the empire of China; one degree more of corruption would have destroyed, perhaps in a single day, the whole human race.
It is not two centuries since the most shameful of all diseases overran Europe, Asia, and Africa; in a very short time it worked terrible havoc; had it continued its progress with unchanging fury, it would have destroyed the race. Burdened with disease from their birth, and incapable of sustaining the duties of society, men would have perished miserably.
How would it have been, had the poison possessed a little more strength, as it would certainly have done, if, fortunately, there had not been found a remedy as powerful as any yet discovered!1 Perhaps that disease, which attacks the organs of generation, would have ended by attacking generation itself.
There are philosophers who distinguish two creations: that of things, and that of man. They cannot believe that matter and created things have been in existence only six thousand years; that during all eternity God delayed His works, and only yesterday began to use His creative power. Was it because He could not, or because He would not? But if He could not at one time, neither could He at another. It is then because He would not; but, as time does not exist for God, if it is granted that He willed a thing once, He willed it always, and from the beginning.
However, all historians speak of a first father: they show us the origin of human nature. Is it not natural to suppose that Adam was saved from some general calamity, as Noah was, from the Flood; and that such great events have been of frequent occurrence since the creation of the world? But all destructions have not been violent. We see many parts of the earth tired out with providing subsistence for men; how do we know that the whole earth has not within itself general causes of debility, slow-working and imperceptible?
It has been a satisfaction to me to give you these general ideas before replying more particularly to your letter on the decrease of mankind which has been going on for seventeen or eighteen centuries. I will show you in a succeeding letter, that moral causes, independently of physical ones, have produced this effect.