Price's two volumes of Observations. Having given some tables on
the probabilities of life, in towns and in the country, he says
(Vol. II, p. 243):

From this comparison, it appears with how much truth great cities
have been called the graves of mankind. It must also convince all
who consider it, that according to the observation, at the end of
the fourth essay, in the former volume, it is by no means
strictly proper to consider our diseases as the original
intention of nature. They are, without doubt, in general our own
creation. Were there a country where the inhabitants led lives
entirely natural and virtuous, few of them would die without
measuring out the whole period of present existence allotted to
them; pain and distemper would be unknown among them, and death
would come upon them like a sleep, in consequence of no other
cause than gradual and unavoidable decay.

I own that I felt myself obliged to draw a very opposite
conclusion from the facts advanced in Dr Price's two volumes. I
had for some time been aware that population and food increased
in different ratios, and a vague opinion had been floating in my
mind that they could only be kept equal by some species of misery
or vice, but the perusal of Dr Price's two volumes of
Observations, after that opinion had been conceived, raised it at
once to conviction. With so many facts in his view to prove the
extraordinary rapidity with which population increases when
unchecked, and with such a body of evidence before him to
elucidate even the manner by which the general laws of nature
repress a redundant population, it is perfectly inconceivable to
me how he could write the passage that I have quoted. He was a