problematically as not impossible to thought, without assuring it
any objective reality, and merely lest the supposed impossibility of
what it must at least allow to be thinkable should endanger its very
being and plunge it into an abyss of scepticism.

Inasmuch as the reality of the concept of freedom is proved by an
apodeictic law of practical reason, it is the keystone of the whole
system of pure reason, even the speculative, and all other concepts
(those of God and immortality) which, as being mere ideas, remain in
it unsupported, now attach themselves to this concept, and by it
obtain consistence and objective reality; that is to say, their
possibility is proved by the fact that freedom actually exists, for
this idea is revealed by the moral law.

Freedom, however, is the only one of all the ideas of the
speculative reason of which we know the possibility a priori (without,
however, understanding it), because it is the condition of the moral
law which we know. * The ideas of God and immortality, however, are
not conditions of the moral law, but only conditions of the necessary
object of a will determined by this law; that is to say, conditions of
the practical use of our pure reason. Hence, with respect to these
ideas, we cannot affirm that we know and understand, I will not say
the actuality, but even the possibility of them. However they are
the conditions of the application of the morally determined will to
its object, which is given to it a priori, viz., the summum bonum.
Consequently in this practical point of view their possibility must be
assumed, although we cannot theoretically know and understand it. To
justify this assumption it is sufficient, in a practical point of
view, that they contain no intrinsic impossibility (contradiction).
Here we have what, as far as speculative reason is concerned, is a