frequently fit, but not rules which must hold good always and
necessarily; hence, no practical laws can be founded on it. Just
because in this case an object of choice is the foundation of the rule
and must therefore precede it, the rule can refer to nothing but
what is [felt], and therefore it refers to experience and is founded
on it, and then the variety of judgement must be endless. This
principle, therefore, does not prescribe the same practical rules to
all rational beings, although the rules are all included under a
common title, namely, that of happiness. The moral law, however, is
conceived as objectively necessary, only because it holds for everyone
that has reason and will.

The maxim of self-love (prudence) only advises; the law of
morality commands. Now there is a great difference between that
which we are advised to do and that to which we are obliged.

The commonest intelligence can easily and without hesitation see
what, on the principle of autonomy of the will, requires to be done;
but on supposition of heteronomy of the will, it is hard and
requires knowledge of the world to see what is to be done. That is
to say, what duty is, is plain of itself to everyone; but what is to
bring true durable advantage, such as will extend to the whole of
one's existence, is always veiled in impenetrable obscurity; and
much prudence is required to adapt the practical rule founded on it to
the ends of life, even tolerably, by making proper exceptions. But the
moral law commands the most punctual obedience from everyone; it must,
therefore, not be so difficult to judge what it requires to be done,
that the commonest unpractised understanding, even without worldly
prudence, should fail to apply it rightly.