The Metaphysics of Morals by Immanuel Kant Chapter 3 Page 32

an end to the discord in which it entangles itself in theoretical questions, so that practical reason may have rest and security from external attacks which might make the ground debatable on which it desires to build.

The claims to freedom of will made even by common reason are founded on the consciousness and the admitted supposition that reason is independent of merely subjectively determined causes which together constitute what belongs to sensation only and which consequently come under the general designation of sensibility. Man considering himself in this way as an intelligence places himself thereby in a different order of things and in a relation to determining grounds of a wholly different kind when on the one hand he thinks of himself as an intelligence endowed with a will, and consequently with causality, and