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