Here’s an excerpt from Richard Tarnas’ “The Passion of the Western Mind”:
Plato described the Ideas not so much as neutral objects of dispassionate rational apprehension but as transcendent essences that, when directly experienced by the pure philosopher, evoke intense emotional response and even mystical rapture. The philosopher is literally a “lover of wisdom” and approaches his intellectual task as a romantic quest of universal significance. For Plato, the ultimate reality is not only ethical and rational in nature, but also aesthetic. The Good, the True, and the Beautiful are effectively united in the supreme creative principle, at once commanding moral affirmation, intellectual allegiance, and aesthetic surrender. As the most accessible of the Forms, visible in part even to the physical eye, Beauty opens up human awareness to the existence of the other Forms, drawing the philosopher toward the beatific vision and knowledge of the True and the Good. Hence Plato suggested that the highest philosophical vision is possible only to one with the temperament of a lover. The philosopher must permit himself to be inwardly grasped by the most sublime form of Eros — that universal passion to restore a former unity, to overcome the separation from the divine and become one with it.
Richard Tarnas, “The Passion of the Western Mind”, p. 41
For Plato, intellectual rigour did not detract from, but rather was integral to, the spiritual path and the apprehension of transcendent reality. Beauty is a sort of gateway transcendental Idea/Essence; its accessibility, in that it can be apprehended in part by the sense of vision, enables it to plant the first seeds of awareness of the timeless and changeless. This gives spiritual context and relevance to artistic and aesthetic endeavours. Apprehension of the divine is at once intellectual, emotional, and mystical, uniting what can otherwise appear to be separate realms of experience.