The Enneads

Having defined eternity and time This refers to the conclusion of the treatise "On Eternity and Time," which Porphyry placed at the end of his initial grouping., he concluded there upon the subject of time. The treatise "On Nature, Contemplation, and the One" is placed here because of the chapter concerning nature. So, while the first Ennead addresses fitting ethical matters, he places the other collections next because they trace back the causes of the world.

1 On the substance of the universe, what it is.
2 On the circular motion of the heavens.
3 On whether the stars are causes. original: "περὶ τῶν ἄστρων εἰ ποιεῖ" — Plotinus argues against astrology in its deterministic form.
4 On substance.
5 On potentiality and actuality. Potentiality and Actuality: Aristotelian terms describing the capacity for change versus the fulfillment of that capacity.
6 On quality and form.
7 On mixture and total penetration.
8 On sight.
9 Against the Gnostics. A famous polemic where Plotinus defends the beauty of the physical world against Gnostic pessimism.

Thus, the second Ennead contains matters concerning the cosmos and the things within it. The third Ennead likewise contains matters regarding the world, focusing on its internal workings and providential order. The contents of the third are as follows:

1 On destiny. original: "περὶ εἱμαρμένης" — often translated as Fate.
2 On providence, book I.
3 On providence, book II.
4 On our allotted guardian spirit. Daemon: in this context, a tutelary spirit or a level of the soul that guides the individual.
5 On love.
6 On the impassibility of the incorporeal.
7 On eternity and time.
8 On nature, contemplation, and the One.
9 On various detached considerations.

These first three Enneads were arranged into a single volume original: "σώματι" — literally "body," here referring to a physical book or scroll-case.. The fourth Ennead was placed after these, containing the systematic treatises on the Soul.

This is what we call the fourth Ennead. Regarding the causes within the same [subject], and those which follow in order from it... fragmented text? knowing the necessary things regarding them. We have arranged the matters of the bodily... the rest of the Enneads. All his writings have been recorded. The fourth Ennead is his; since the works of the third body were arranged in Enneads. These are the things concerning the Enneads... concerning the origins of the soul. The titles are these:

1 On the essence of the soul, book I.
2 On the essence of the soul, book II.
3 On difficulties concerning the soul, book I.
4 On difficulties concerning the soul, book II.
5 On difficulties concerning the soul, book III, or "On Sight."
6 On sense-perception and memory.
7 On the immortality of the soul.
8 On the descent of the soul into bodies.
9 Whether all souls are one.

The fifth Ennead was placed after this one, containing the treatises on the Intellect. Intellect: (Greek: Nous) The second principle in Plotinus's system, the realm of pure thought and the Platonic Ideas. The titles are these:

1 On the three primary hypostases. original: "ὑποστάσεων" — foundational levels of reality (the One, Intellect, and Soul).
2 On the origin and order of things after the First.
3 On the knowing hypostases and that which is beyond.
4 How that which follows the First comes from the First, and on the One.
5 That the objects of thought are not outside the Intellect, and on the Good.
6 On that which is beyond the Intellect, and what is the primary and secondary thinker.
7 On whether there are Ideas of individual beings.
8 On intelligible beauty.
9 On the Intellect, the Ideas, and Being.

These five Enneads we have arranged into two volumes. We have arranged the sixth Ennead in another volume, so that through the six Enneads the fifty-four treatises might be written across three volumes. Although the subjects might seem to cause wandering to some, these are the headings of all these matters. Again, concerning the divisions of all things, the books of temporal substances have been shown. Now, furthermore...