Everything in nature acts in conformity with law.

Natural science physics contains in itself synthetical judgments a priori, as principles. ... Space then is a necessary representation a priori, which serves for the foundation of all external intuitions.

Things which we see are not by themselves what we see ... It remains completely unknown to us what the objects may be by themselves and apart from the receptivity of our senses. We know nothing but our manner of perceiving them.

In every department of physical science there is only so much science, properly so-called, as there is mathematics.

Imagination is a powerful agent for creating, as it were, a second nature out of the material supplied to it by actual nature.

[S]uppose the mind of [a] friend of humanity were clouded over with his own grief, extinguishing all sympathetic participation in the fate of others; he still has the resources to be beneficent to those suffering distress, but the distress of others does not touch him because he is sufficiently busy with his own; and now, where no inclination any longer stimulates him to it, he tears himself out of his deadly insensibility and does the action without any inclination, solely from duty.

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.