The Metaphysics of Morals by Immanuel Kant Chapter 3 Page 33

when on the other he perceives himself as a phenomenon in the world of sense (as he really is also), and affirms that his causality is subject to external determination according to laws of nature.

Now he soon becomes aware that both can hold good, nay, must hold good at the same time. For there is not the smallest contradiction in saying that a thing in appearance (belonging to the world of sense) is subject to certain laws, of which the very same as a thing or being in itself is independent, and that he must conceive and think of himself in this twofold way, rests as to the first on the consciousness of himself as an object affected through the senses, and as to the second on the consciousness of himself as an intelligence, i.e., as independent on sensible impressions in the employment of his reason