The radiance of which he speaks is the scholastic quidditas, the whatness of a thing. This supreme quality is felt by the artist when the aesthetic image is first conceived in his imagination. The mind in that mysterious instant Shelley likened beautifully to a fading coal. The instant wherein that supreme quality of beauty, the clear radiance of the aesthetic image, is apprehended luminously by the mind which has been arrested by its wholeness and fascinated by its harmony is the luminous silent stasis of aesthetic pleasure, a spiritual state very like to that cardiac condition which the Italian physiologist Luigi Galvani, using a phrase almost as beautiful as Shelley's, called the enchantment of the heart.