CHAPTER 9.
Mr Condorcet's conjecture concerning the organic perfectibility of man, and the indefinite prolongation of human life--Fallacy of the argument, which infers an unlimited progress from a partial improvement, the limit of which cannot be ascertained, illustrated in the breeding of animals, and the cultivation of plants.
The last question which Mr Condorcet proposes for examination is the organic perfectibility of man.

He observes that if the proofs which have been already given and which, in their development will receive greater force in the work itself, are sufficient to establish the indefinite perfectibility of man upon the supposition of the same natural faculties and the same organization which he has at present, what will be the certainty, what the extent of our hope, if this organization, these natural faculties themselves, are susceptible of amelioration?
From the improvement of medicine, from the use of more wholesome food and habitations, from a manner of living which will improve the strength of the body by exercise without impairing it by excess, from the destruction of the two great causes of the degradation of man, misery, and too great riches, from the gradual removal of transmissible and contagious disorders by the improvement of physical knowledge, rendered more efficacious by the progress of reason and of social order, he infers that though man will not absolutely become immortal, yet that the duration between his birth and natural death will increase without ceasing, will have no assignable term, and may properly be expressed by the word 'indefinite'.

He then defines this word to mean either a constant approach to an unlimited extent, without ever reaching it, or an increase.

In the immensity of ages to an extent greater than any assignable quantity.
But surely the application of this term in either of these senses to the duration of human life is in the highest degree unphilosophical and totally unwarranted by any appearances in the laws of nature.
Variations from different causes are essentially distinct from a regular and unretrograde increase.

The average duration of human life will to a certain degree vary from healthy or unhealthy climates, from wholesome or unwholesome food, from virtuous or vicious manners, and other causes, but it may be fairly doubted whether there is really the smallest perceptible advance in the natural duration of human life since first we have had any authentic history of man.