Reason must approach nature with the view, indeed, of receiving information from it, not, however, in the character of a pupil, who listens to all that his master chooses to tell him, but in that of a judge, who compels the witnesses to reply to those questions which he himself thinks fit to propose. To this single idea must the revolution be ascribed, by which, after groping in the dark for so many centuries, natural science was at length conducted into the path of certain progress.
Every man is to be respected as an absolute end in himself; and it is a crime against the dignity that belongs to him as a human being, to use him as a mere means for some external purpose.
We ourselves introduce that order and regularity in the appearance which we entitle "nature". We could never find them in appearances had we not ourselves, by the nature of our own mind, originally set them there.
Aus so krummen Holze, als woraus der Mensch gemacht ist, kann nichts ganz Gerades gezimmert werden. Out of the crooked timber of humanity, no straight thing can ever be made.