would support as large a head as a cabbage.

The reasons of the mortality of plants are at present
perfectly unknown to us. No man can say why such a plant is
annual, another biennial, and another endures for ages. The whole
affair in all these cases, in plants, animals, and in the human
race, is an affair of experience, and I only conclude that man is
mortal because the invariable experience of all ages has proved
the mortality of those materials of which his visible body is
made:

What can we reason, but from what we know?

Sound philosophy will not authorize me to alter this opinion
of the mortality of man on earth, till it can be clearly proved
that the human race has made, and is making, a decided progress
towards an illimitable extent of life. And the chief reason why I
adduced the two particular instances from animals and plants was
to expose and illustrate, if I could, the fallacy of that
argument which infers an unlimited progress, merely because some
partial improvement has taken place, and that the limit of this
improvement cannot be precisely ascertained.

The capacity of improvement in plants and animals, to a
certain degree, no person can possibly doubt. A clear and decided
progress has already been made, and yet, I think, it appears that
it would be highly absurd to say that this progress has no
limits. In human life, though there are great variations from
different causes, it may be doubted whether, since the world
began, any organic improvement whatever in the human frame can be