The relation which the several parts or members of the natural body
have to each other and to the whole body is here compared to the
relation which each particular person in society has to other
particular persons and to the whole society; and the latter is
intended to be illustrated by the former. And if there be a
likeness between these two relations, the consequence is obvious:
that the latter shows us we were intended to do good to others, as
the former shows us that the several members of the natural body
were intended to be instruments of good to each other and to the
whole body. But as there is scarce any ground for a comparison
between society and the mere material body, this without the mind
being a dead unactive thing, much less can the comparison be carried
to any length. And since the apostle speaks of the several members
as having distinct offices, which implies the mind, it cannot be
thought an allowable liberty, instead of the BODY and ITS MEMBERS,
to substitute the WHOLE NATURE of MAN, and ALL THE VARIETY OF
INTERNAL PRINCIPLES WHICH BELONG TO IT. And then the comparison
will be between the nature of man as respecting self, and tending to
private good, his own preservation and happiness; and the nature of
man as having respect to society, and tending to promote public
good, the happiness of that society. These ends do indeed perfectly
coincide; and to aim at public and private good are so far from
being inconsistent that they mutually promote each other: yet in
the following discourse they must be considered as entirely
distinct; otherwise the nature of man as tending to one, or as
tending to the other, cannot be compared. There can no comparison
be made, without considering the things compared as distinct and
different.

From this review and comparison of the nature of man as respecting