{BOOK_1|CHAPTER_1 ^paragraph 145}
We have in the moral principle set forth a law of causality, the
determining principle of which is set above all the conditions of
the sensible world; we have it conceived how the will, as belonging
to the world, is determinable, and therefore have
its subject (man) not merely conceived as belonging to a world of
pure understanding, and in this respect unknown (which the critique of
speculative reason enabled us to do), but also defined as regards
his causality by means of a law which cannot be reduced to any
physical law of the sensible world; and therefore our knowledge is
extended beyond the limits of that world, a pretension which the
Critique of Pure Reason declared to be futile in all speculation.
We have in the moral principle set forth a law of causality, the
determining principle of which is set above all the conditions of
the sensible world; we have it conceived how the will, as belonging
to the world, is determinable, and therefore have
its subject (man) not merely conceived as belonging to a world of
pure understanding, and in this respect unknown (which the critique of
speculative reason enabled us to do), but also defined as regards
his causality by means of a law which cannot be reduced to any
physical law of the sensible world; and therefore our knowledge is
extended beyond the limits of that world, a pretension which the
Critique of Pure Reason declared to be futile in all speculation.
Kant - Critique of Practical Reason
