At the outset of the eighteenth century, genius was characterized simply as exceptional facility in perception and representation, where the latter is the object of artistic production and the former its precondition. As the century progressed, and as long into the nineteenth century as genius remained a lively topic, it came to be characterized as a gift for invention, leading to originality in artistic representation. But only by a few, whom we might for this reason call philosophical geniuses, were the implications of the new conception of genius fully embraced. Immanuel Kant was the first to recognize that genius, as exemplary originality, would be a stimulus and provocation to continuing revolution in the history of art; and John Stuart Mill, inspired by Wilhelm von Humboldt, was the first to argue that the expression of individuality in such a form is good in and of itself. What led Kant to his position was a distinctive conception of aesthetic experience and thus of the aims of art; what led Mill to his was a distinctive conception of the human good in general. In what follows, I will bring out what is distinctive in their conceptions of genius by contrasting them with those of other apostles of genius, such as Alexander Gerard, Samuel Taylor Coleridge, and Ralph Waldo Emerson, whose conceptions of genius were not in fact as radical as those of Kant and Mill.