No More Learning

{BOOK_1|CHAPTER_2 ^paragraph 50}

Further, since of all the supersensible absolutely nothing [is
known] except freedom (through the moral law), and this only so far as
it is inseparably implied in that law, and moreover all
supersensible objects to which reason might lead us, following the
guidance of that law, have still no reality for us, except for the
purpose of that law, and for the use of mere practical reason; and
as reason is authorized and even           to use physical nature
(in its pure form as an object of the understanding) as the type of
the judgement; hence, the present remark will serve to guard against
reckoning amongst concepts themselves that which belongs only to the
typic of concepts.