No-one can compel me to be happy in accordance with his conception of the welfare of others, for each may seek his happiness in whatever way he sees fit, so long as he does not infringe upon the freedom of others to pursue a similar end which can be reconciled with the freedom of everyone else within a workable general law ? i.e. he must accord to others the same right as he enjoys himself.
The light dove, in free flight cutting through the air the resistance of which it feels, could get the idea that it could do even better in airless space. Likewise, Plato abandoned the world of the senses because it posed so many hindrances for the understanding, and dared to go beyond it on the wings of the ideas, in the empty space of pure understanding.
The universal and lasting establishment of peace constitutes not merely a part, but the whole final purpose and end of the science of right as viewed within the limits of reason.
Enlightenment is man's leaving his self-caused immaturity. Immaturity is the incapacity to use one's intelligence without the guidance of another. Such immaturity is self-caused if it is not caused by lack of intelligence, but by lack of determination and courage to use one's intelligence without being guided by another. Sapere Aude! Have the courage to use your own intelligence! is therefore the motto of the enlightenment.
The evil effect of science upon men is principally this, that by far the greatest number of those who wish to display a knowledge of it accomplish no improvement at all of the understanding, but only a perversity of it, not to mention that it serves most of them as a tool of vanity.
In the metaphysical elements of aesthetics the various nonmoral feelings are to be made use of; in the elements of moral metaphysics the various moral feelings of men, according to the differences in sex, age, education, and government, of races and climates, are to be employed.
Moral Teleology supplies the deficiency in physical Teleology , and first establishes a Theology ; because the latter, if it did not borrow from the former without being observed, but were to proceed consistently, could only found a Demonology , which is incapable of any definite concept.