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

Freedom is the alone unoriginated birthright of man, and belongs to him by force of his humanity.

The bad thing of war is, that it makes more evil people than it can take away.

Religion is the recognition of all our duties as divine commands.

Enthusiasm is always connected with the senses, whatever be the object that excites it. The true strength of virtue is serenity of mind, combined with a deliberate and steadfast determination to execute her laws. That is the healthful condition of the moral life; on the other hand, enthusiasm, even when excited by representations of goodness, is a brilliant but feverish glow which leaves only exhaustion and languor behind.

The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.

Time is not an empirical concept. For neither co-existence nor succession would be perceived by us, if the representation of time did not exist as a foundation a priori.