The second treats of the effect resulting both to art and religion from the expression of mystical and theological conceptions in plastic form.
When we consider the nature of the ideas assimilated in the Middle Ages by the human mind, it is clear that art, in order to set them forth, demanded a language the Greeks had never greatly needed, and had therefore never fully learned.

To over-estimate the difference from an aesthetic point of view between the religious notions of the Greeks and those which Christianity had made essential, would be difficult.

Faith, hope, and charity; humility, endurance, suffering; the Resurrection and the Judgment; the Pall and the Redemption; Heaven and Hell; the height and depth of man's mixed nature; the drama of human destiny before the throne of God: into the sphere of thoughts like these, vivid and solemn, transcending the region of sense and corporeity, carrying the mind away to an ideal world, where the things of this earth obtained a new reality by virtue of their relation to an invisible and infinite Beyond, the modern arts in their infancy were thrust.

There was nothing finite here or tangible, no gladness in the beauty of girlish foreheads or the swiftness of a young man's limbs, no simple idealisation of natural delightfulness.
The human body, which the figurative arts must needs use as the vehicle of their expression, had ceased to have a value in and for itself, had ceased to be the true and adequate investiture of thoughts demanded from the artist.

At best it could be taken only as the symbol of some inner meaning, the shrine of an indwelling spirit nobler than itself; just as a lamp of alabaster owes its beauty and its worth to the flame it more than half conceals, the light transmitted through its scarce transparent walls.
In ancient art those moral and spiritual qualities which the Greeks recognised as truly human and therefore divine, allowed themselves to be incarnated in well-selected types of physical perfection.