Positively, it can be shown that, granted the outlines of Plotinus’ view of the world, there must be intermediaries between the Noûs and the sensible world. And vet it must be admitted that, as our insight into the nature of soul progressively deepens, there seems to be a danger that soul, in the real order, will be seen to be absorbed into Noûs on the one hand and into the sensible world on the other.
We are first told that soul, the highest part of which is rooted in the intelligible world, descends to the sensible as the bearer of logos. This descending to the sensible is the producing of the sensible. The more soul descends, the less real, the less contemplative, the less productive it becomes. Nature, the lowest part of soul, the least productively contemplative, produces the lowest reality, the sensible cosmos.
And yet how can soul, insofar as it is rooted in the world of true being, actually descend? It cannot: Plotinus says in one place that it “appears to descend.” The “descent” of soul is a metaphor; it can be balanced by another metaphor: the lower reaches for the higher, matter attempts to seize being and intelligibility. Perhaps nature as contemplation is rather the result of an effort from below. It is, perhaps, the imitation being and intelligibility which matter has seized for itself.
Yet the notion of matter “trying to seize” being is metaphorical. Matter has no power. What appears to be present in matter is present because of the productive power of the Noûs. Therefore, if in truth there is no descent, and if there is no effort from below, perhaps soul is merely Noûs considered as related (although Noûs actually is not related) to the visible cosmos. A similar explanation might be applied to the lower “parts” of soul. In this case nature would be Noûs considered as related to plants, the earth, and the vegetative functions in animals.
If the higher part of soul is in the intelligible world, is it in any way distinct from Noûs? Is not “soul” an unnecessary term for something which is really Noûs? And what of the “lower part”? If it is not Noûs, it would seem to be purely sensible, purely imitation, cut off from Noûs and being, indistinguishable therefore from the sensible world. And thus soul would disappear as an hypostasis. Soul and nature would be only logically distinct from Noûs, and there would be, in the real order, only the Noûs and the sensible world.
Plotinus, however, neither says this nor means this. For him, soul is an hypostasis, a nature, a reality, really distinct from Noûs; thus nature, as the lower part of soul, would be distinct from Noûs as a distinct hypostasis—or part of a distinct hypostasis. The world contains whatever is, to any degree, real. Further, there is for Plotinus a rigorous correspondence between thought and thing. If the world can be known in a certain way, that is because it is in a certain way. If it is in a certain way, it can be known in that way.
Thus there is not only sense and intellect; not only the imitation world and the world of true being. The world can be known as Noûs, as true being. But it can be known also as Noûs with a mission to form and order matter, therefore no longer perfectly as Noûs, but as soul—and this is to know something real. And again, the world can be known as soul no longer capable of producing within itself, but capable only of producing upon matter—this again is to know something real, nature.