Our further experience has given us some little insight into these causes, and has therefore enabled us better to judge, if not of what we are to expect in future, at least of what we are not to expect, which, though negative, is a very useful piece of information.
As the necessity of sleep seems rather to depend upon the body than the mind, it does not appear how the improvement of the mind can tend very greatly to supersede this 'conspicuous infirmity'.

A man who by great excitements on his mind is able to pass two or three nights without sleep, proportionably exhausts the vigour of his body, and this diminution of health and strength will soon disturb the operations of his understanding, so that by these great efforts he appears to have made no real progress whatever in superseding the necessity of this species of rest.
There is certainly a sufficiently marked difference in the various characters of which we have some knowledge, relative to the energies of their minds, their benevolent pursuits, etc., to enable us to judge whether the operations of intellect have any decided effect in prolonging the duration of human life.

It is certain that no decided effect of this kind has yet been observed.

Though no attention of any kind has ever produced such an effect as could be construed into the smallest semblance of an approach towards immortality, yet of the two, a certain attention to the body seems to have more effect in this respect than an attention to the mind.

The man who takes his temperate meals and his bodily exercise, with scrupulous regularity, will generally be found more healthy than the man who, very deeply engaged in intellectual pursuits, often forgets for a time these bodily cravings.