promote as my end, it must be the happiness of other men whose
(permitted) end I hereby make also mine. It still remains left to
themselves to decide what they shall reckon as belonging to their
happiness; only that it is in my power to decline many things which
they so reckon, but which I do not so regard, supposing that they have
no right to demand it from me as their own. A plausible objection
often advanced against the division of duties above adopted consists
in setting over against that end a supposed obligation to study my own
(physical) happiness, and thus making this, which is my natural and
merely subjective end, my duty (and objective end). This requires to
be cleared up.

Adversity, pain, and want are great temptations to transgression
of one's duty; accordingly it would seem that strength, health, a
competence, and welfare generally, which are opposed to that
influence, may also be regarded as ends that are also duties; that is,
that it is a duty to promote our own happiness not merely to make that
of others our end. But in that case the end is not happiness but the
morality of the agent; and happiness is only the means of removing the
hindrances to morality; permitted means, since no one has a right to
demand from me the sacrifice of my not immoral ends. It is not
directly a duty to seek a competence for one's self; but indirectly it
may be so; namely, in order to guard against poverty which is a
great temptation to vice. But then it is not my happiness but my
morality, to maintain which in its integrity is at once my end and
my duty.

{INTRODUCTION ^paragraph 55}