supersensible nature, so far as we can form any notion of it, is
nothing else than a system of nature under the autonomy of pure
practical reason. Now, the law of this autonomy is the moral law,
which, therefore, is the fundamental law of a supersensible nature,
and of a pure world of understanding, whose counterpart must exist
in the world of sense, but without interfering with its laws. We might
call the former the archetypal world (natura archetypa), which we only
know in the reason; and the latter the ectypal world (natura
ectypa), because it contains the possible effect of the idea of the
former which is the determining principle of the will. For the moral
law, in fact, transfers us ideally into a system in which pure reason,
if it were accompanied with adequate physical power, would produce the
summum bonum, and it determines our will to give the sensible world
the form of a system of rational beings.

The least attention to oneself proves that this idea really serves
as the model for the determinations of our will.

When the maxim which I am disposed to follow in giving testimony
is tested by the practical reason, I always consider what it would
be if it were to hold as a universal law of nature. It is manifest
that in this view it would oblige everyone to speak the truth. For
it cannot hold as a universal law of nature that statements should
be allowed to have the force of proof and yet to be purposely
untrue. Similarly, the maxim which I adopt with respect to disposing
freely of my life is at once determined, when I ask myself what it
should be, in order that a system, of which it is the law, should
maintain itself. It is obvious that in such a system no one could
arbitrarily put an end to his own life, for such an arrangement
would not be a permanent order of things. And so in all similar cases.