MacKenna-Plotinus: Act of the Intellect

But how can I form the conception of the sizelessness of Matter? How do you form the concept of any absence of quality? What is the Act of the Intellect, what is the mental approach, in such a case? The secret is Indetermination. Enneads   II,4,10

Soul, then, is one and many - as many as are manifested in that oneness - one in its nature, many in those other things. A single Existent, it makes itself many by what we may call its motion: it is one entire, but by its striving, so to speak, to contemplate itself, it is a plurality; for we may imagine that it cannot bear to be a single Existent, when it has the power to be all that it in fact is. The cause of its appearing as many is this contemplation, and its purpose is the Act of the Intellect; if it were manifested as a bare unity, it could have no intellection, since in that simplicity it would already be identical with the object of its thought. Enneads VI,2,6

No doubt there is the passage "Whatever Intellect sees in the entire Life-Form"; thus seeing, must not the Intellectual-Principle be the later? No; the seeing may imply merely that the reality comes into being by the fact of that seeing; the Intellectual-Principle is not external to the Life-Form; all is one; the Act of the Intellectual-Principle possesses itself of bare sphere, while the Life-Form holds the sphere as sphere of a living total. Enneads VI,6,17