essentially identical with this other: "Act upon a maxim which, at the
same time, involves its own universal validity for every rational
being." For that in using means for every end I should limit my
maxim by the condition of its holding good as a law for every subject,
this comes to the same thing as that the fundamental principle of
all maxims of action must be that the subject of all ends, i.e., the
rational being himself, be never employed merely as means, but as
the supreme condition restricting the use of all means, that is in
every case as an end likewise.

It follows incontestably that, to whatever laws any rational being
may be subject, he being an end in himself must be able to regard
himself as also legislating universally in respect of these same laws,
since it is just this fitness of his maxims for universal
legislation that distinguishes him as an end in himself; also it
follows that this implies his dignity (prerogative) above all mere
physical beings, that he must always take his maxims from the point of
view which regards himself and, likewise, every other rational being
as law-giving beings (on which account they are called persons). In
this way a world of rational beings (mundus intelligibilis) is
possible as a kingdom of ends, and this by virtue of the legislation
proper to all persons as members. Therefore every rational being
must so act as if he were by his maxims in every case a legislating
member in the universal kingdom of ends. The formal principle of these
maxims is: "So act as if thy maxim were to serve likewise as the
universal law (of all rational beings)." A kingdom of ends is thus
only possible on the analogy of a kingdom of nature, the former
however only by maxims, that is self-imposed rules, the latter only by
the laws of efficient causes acting under necessitation from
without. Nevertheless, although the system of nature is looked upon as