According to Paul Guyer, line between the aesthetic and the ethical got drawn in the 18th century. Here’s an excerpt from Guyer’s essay, “Ethical Value of the Aesthetic: Kant, Alison, and Santayana,” (Chapter 8; Values of Beauty: Historical Essays in Aesthetics):
The separation of the aesthetic and the ethical is usually thought to have been introduced into modern philosophy in the eighteenth century by such thinkers as the Third Earl of Shaftesbury and Francis Hutchinson, but above all by Immanuel Kant, whose “Analytic of the Beautiful” in his third great critique, the Critique of the Power of Judgement of 1790, opens with the claim that the “satisfaction that determines the judgement of taste is without any interest,” thus that the satisfaction “of the taste for the beautiful is a disinterested and free satisfaction; for no interest, neither that of the senses, nor that of reason, extorts approval.”But Kant has also emphasized there are several ways by which the aesthetic can facilitate the achievement of morality while not being indispensable to that effort. Here’s Guyer’s perspective on this point:
Kant’s assertion of the disinterestedness of judgements of taste is only the beginning of a complex analysis of aesthetic experience, aesthetic judgement, and the nature of art, which ends up by drawing a large number of beneficial connections between aesthetic experience and moral conduct. Kant thus undermines the idea that there can or should be a rigid barrier between the aesthetic and ethical even before it gets off the ground and indeed introduces some connections between them…The harmony that we find in the content, form, and material of the successful works of fine arts is according to Kant capable of inspiring ethical values. He suggests that aesthetic experience can be conducive to the development of sound politics as well as personal ethics.