Even if a civil society were to be dissolved by the consent of all its members (e.g., if a people inhabiting an island decided to separate and disperse throughout the world), the last murderer remaining in prison would first have to be executed, so that each has done to him what his deeds deserve and blood guilt does not cling to the people for not having insisted upon this punishment; for otherwise the people can be regarded as collaborators in his public violation of justice.
A philosophical attempt to work out a universal history according to a natural plan directed to achieving the civic union of the human race must be regarded as possible and, indeed, as contributing to this end of Nature.
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.
Enlightenment is man's emergence from his self-imposed immaturity...No thing is required for this enlightenment.. .except freedom; and the freedom in question is the least harmful of all, namely, the freedom to use reason publicly in all matters.
We find that the more a cultivated reason devotes itself to the aim of enjoying life and happiness, the further does man get away from true contentment.
The sceptics, a kind of nomads, despising all settled culture of the land, broke up from time to time all civil society. Fortunately their number was small, and they could not prevent the old settlers from returning to cultivate the ground afresh, though without any fixed plan or agreement.
Manners or etiquette ('accessibility, affability, politeness, refinement, propriety, courtesy, and ingratiating and captivating behavior') call for no large measure of moral determination and cannot, therefore, be reckoned as virtues. Even though manners are no virtues, they are a means of developing virtue.... The more we refine the crude elements in our nature, the more we improve our humanity and the more capable it grows of feeling the driving force of virtuous principles.
In man (as the only rational creature on earth) those natural capacities which are directed to the use of his reason are to be fully developed only in the race, not in the individual.
Even the song of birds, which we can bring under no musical rule, seems to have more freedom, and therefore more for taste, than a song of a human being which is produced in accordance with all the rules of music; for we very much sooner weary of the latter, if it is repeated often and at length. Here, however, we probably confuse our participation in the mirth of a little creature that we love, with the beauty of its song; for if this were exactly imitated by man (as sometimes the notes of the nightingale are) it would seem to our ear quite devoid of taste.