The Neo-Platonist axiom that the many proceeds from the one might first be understood in the sense of units: we can only get a bunch of X’s by having one X at a time. This takes “the one” in the axiom in terms of the material causality of a parts making a whole. But the axiom is both meant to be self-evident, and to yield more interesting results, when considered in the other modes of causality.
The objects of a discourse are many, but there is something making them one. This happens self-evidently when “the one” is taken as the human mind, which gathers together, say, all living things to form biology. But this would only explain how the objects could be known by us, not how they could be discovered. The unity among the living is not made by us in every way, but is also found in things. Just as we have insight into a source of knowledge from the procession of the known multitude from the separate one, so too there is an insight into a source of existence from the procession of the existent multitude from the from the separate one.
This source of the existence we discover in things is outside of all discourse about multitude. It is not an item either enumerated or capable of enumeration. We find in it a sort of individuality which we too often erroneously attribute in an absolute sense to ourselves, since for us total uniqueness would be alienation. The source of existence is not knowable by us insofar as all that is known by us is repeatable: even the one sun we know can be imagined as happening many times.
The one that is a source of existence is not in time, for all that is in time is not only identified but re-identified. It is not in space, for whatever exists in such a way is the same as whatever might replace it where it is.
The one is a reflection of intelligence: it gives the unity in discourse that is discovered by our mind. There is therefore something of mind in it so far as mind is an echo and sympathy with its work, but it is not a mind beholding things as though they could be discovered by it.
In addition to the more ancient insights into the one given here: qualified but very real unknowability, eternity, non-temporality, there is a need to incorporate new insights about the value of novelty and surprise in its knowledge, and the transcendental perfection of the second-person point of view, and the perfections of diverse personalities.