The categories of the second class (those of causality and of the
necessity of a thing) did not require this homogeneity (of the
conditioned and the condition in synthesis), since here what we have to
explain is not how the intuition is compounded from a manifold in it,
but only how the existence of the conditioned object corresponding to it
is added to the existence of the condition (added, namely, in the
understanding as connected therewith); and in that case it was allowable
to suppose in the supersensible world the unconditioned to
the altogether conditioned in the world of sense (both as regards the
causal connection and the contingent existence of things themselves),
although this unconditioned remained indeterminate, and to make the
synthesis transcendent.
necessity of a thing) did not require this homogeneity (of the
conditioned and the condition in synthesis), since here what we have to
explain is not how the intuition is compounded from a manifold in it,
but only how the existence of the conditioned object corresponding to it
is added to the existence of the condition (added, namely, in the
understanding as connected therewith); and in that case it was allowable
to suppose in the supersensible world the unconditioned to
the altogether conditioned in the world of sense (both as regards the
causal connection and the contingent existence of things themselves),
although this unconditioned remained indeterminate, and to make the
synthesis transcendent.
Kant - Critique of Practical Reason
