is the best fitted to express the nature of her descent from the higher principle; and on one occasion he illustrates the relation of his three divine substances to one another by the famous figure of a central point representing the One, a fixed circle round that point representing the Nous, and outside that, again, a revolving circle representing the Soul.[475] Still, the different parts of the system are very awkwardly pieced together at this juncture; for the creative energy of the Nous has already been invoked to account for the Ideas or partial intelligences into which it spontaneously divides; and one does not understand how it can be simultaneously applied to the production of something that is not an Idea at all. Fresh difficulties arise in explaining the activity which the Soul, in her turn, exerts. As originally conceived, her function was sufficiently clear. Mediating between two worlds, she transforms the lower one into a likeness of the higher, stamping on material objects a visible image of the eternal Ideas revealed to her by a contemplation of the Nous. And, as a further elaboration of this scheme, we were told that the primary soul generates an inferior soul, which, again, subdivides itself into the multitude of partial souls required for the animation of different bodily organisms. But now that our philosopher has entered on a synthetic construction of the elements furnished by his preliminary analysis, he finds himself confronted by an entirely new problem. For his implied principle is that each hypostasis must generate the grade which comes next after it in the descending series of manifestations, until the possibilities of existence have been exhausted. But in developing and applying the noetic Ideas, the Soul, apparently, finds a pre-existing Matter ready to hand. Thus she has to deal with something lower than herself, which she did not create, and which is not created by the Forms combined with it in sensible experience. We hear of a descent from thought to feeling, and from feeling to simple vitality,[476] but in each instance the depth of the Soul’s fall is measured by the extent to which she penetrates into the recesses of a substance not clearly related to her nor to anything above her.