"There is . . . but one categorical imperative, namely, this: Act only on that maxim whereby thou canst at the same time will that it should become a universal law. . . . Since the universality of the law according to which effects are produced constitutes what is properly called nature in the most general sense (as to form), that is the existence of things so far as it is determined by general laws, the imperative of duty may be expressed thus: Act as if the maxim of thy action were to become by thy will a universal law of nature.
We will now enumerate a few duties, adopting the usual division of them into duties to ourselves and ourselves and to others, and into perfect and imperfect duties.*
1. A man reduced to despair by a series of misfortunes
feels wearied of life, but is still so far in possession of his reason that
he can ask himself whether it would not be contrary to his duty to himself
to take his own life. Now he inquires whether the maxim of his
action could become a universal law of nature. His maxim is: "From
self-love I adopt it as a principle to shorten my life when its
longer duration is likely to bring more evil than satisfaction." It is
asked then simply whether this principle founded on self-love can
become a universal law of nature. Now we see at once that a system of
nature of which it should be a law to destroy life by means of
the very feeling whose special nature it is to impel to the improvement of
life would contradict itself and, therefore, could not exist as
a system of nature; hence that maxim cannot possibly exist as a universal
law of nature and, consequently, would be wholly
inconsistent with the supreme principle of all duty.
2. Another finds himself forced by necessity to borrow
money. He knows
that he will not be able to repay it, but sees also that
nothing will be lent to him unless he promises stoutly to repay it in a
definite time. He desires to make this promise, but he has still
so much conscience as to ask himself: "Is it not unlawful and inconsistent
with duty to get out of a difficulty in this way?" Suppose
however that he resolves to do so: then the maxim of his action would be
expressed thus: "When I think myself in want of money, I
will borrow money and promise to repay it, although I know that I never
can do so." Now this principle of self-love or of one's own
advantage may perhaps be consistent with my whole future welfare; but the
question now is, "Is it right?" I change then the
suggestion of self-love into a universal law, and state the question thus:
"How would it be if my maxim were a universal law?" Then I
see at once that it could never hold as a universal law of nature, but
would necessarily contradict itself. For supposing it to be a
universal law that everyone when he thinks himself in a difficulty should
be able to promise whatever he pleases, with the purpose of
not keeping his promise, the promise itself would become impossible, as
well as the end that one might have in view in it, since no
one would consider that anything was promised to him, but would ridicule
all such statements as vain pretences.
3. A third finds in himself a talent which with the help
of some culture might make him a useful man in many respects. But he finds
himself in comfortable circumstances and prefers to indulge in pleasure
rather than to take pains in enlarging and improving his
happy natural capacities. He asks, however, whether his maxim of neglect
of his natural gifts, besides agreeing with his inclination
to indulgence, agrees also with what is called duty. He sees then that a
system of nature could indeed subsist with such a universal
law although men (like the South Sea islanders) should let their talents
rest and resolve to devote their lives merely to idleness,
amusement, and propagation of their species- in a word, to enjoyment; but
he cannot possibly will that this should be a universal law
of nature, or be implanted in us as such by a natural instinct. For, as a
rational being, he necessarily wills that his faculties be
developed, since they serve him and have been given him, for all sorts of
possible purposes.
4. A fourth, who is in prosperity, while he sees that
others have to contend with great wretchedness and that he could help them,
thinks: "What concern is it of mine? Let everyone be as happy as Heaven
pleases, or as be can make himself; I will take nothing
from him nor even envy him, only I do not wish to contribute anything to
his welfare or to his assistance in distress!" Now no doubt if
such a mode of thinking were a universal law, the human race might very
well subsist and doubtless even better than in a state in
which everyone talks of sympathy and good-will, or even takes care
occasionally to put it into practice, but, on the other side, also
cheats when he can, betrays the rights of men, or otherwise violates them.
But although it is possible that a universal law of nature
might exist in accordance with that maxim, it is impossible to will that
such a principle should have the universal validity of a law of
nature. For a will which resolved this would contradict itself, inasmuch
as many cases might occur in which one would have need of
the love and sympathy of others, and in which, by such a law of nature,
sprung from his own will, he would deprive himself of all hope
of the aid he desires.
These are a few of the many actual duties, or at least what we regard
as such, which obviously fall into two classes on the one
principle that we have laid down. We must be able to will that a maxim of
our action should be a universal law. This is the canon of
the moral appreciation of the action generally. Some actions are of such a
character that their maxim cannot without contradiction
be even conceived as a universal law of nature, far from it being possible
that we should will that it should be so. In others this
intrinsic impossibility is not found, but still it is impossible to will
that their maxim should be raised to the universality of a law of
nature, since such a will would contradict itself. It is easily seen that
the former violate strict or rigorous (inflexible) duty; the latter
only laxer (meritorious) duty. . ."