This treatise is concerned with the relation between Intellect and the Forms, together constituting Being. Here, Plotinus confronts Epicureans and Stoics on their denial of the existence of an intelligible realm that is separate from the sensible. He aims to explain the relations among Forms and their relation to Intellect and how the intelligible world is supposed to serve an ineliminable explanatory role for the sensible world. The sketchiness of the discussion of many points here anticipates the much longer discussions in later treatises. In this regard, it is to be noted that Plotinus does not discuss in this treatise except in passing the first principle of all.
§1. The superiority of Platonism to Epicureanism and Stoicism in explanatory power.
§2. The ascent from the sensible to the intelligible.
§3. An argument for the necessary existence of Intellect and intelligibles.
§4. The superiority of Intellect to Soul and Soul’s dependence on Intellect.
§5. The eternity of Intellect’s intellection of Forms which are internal to it. Sensibles participate in intelligibles.
§6. Intellect’s identity with all intelligibles and their distinctness from each other and from it.
§7. The objects of primary knowledge are Forms. Forms are prior to Intellect and not created by it.
§8. Being consists in Intellect and the Forms which are identical.
§9. Intellect is identical with all that is intelligible. There could be nothing that is not in Intellect paradigmatically.
§10. Everything that has a measure of intelligibility in the sensible world has its paradigm in the intelligible world. There is, however, no evil in the intelligible world.
§11. The sense in which artefacts and crafts can be said to be in the intelligible world.
§12. Are there Forms of individuals? Answer to this question deferred until later (cf. 5.7 (18)).
§13. The sense in which souls are and are not in the intelligible world.
§14. There are not Forms for everything in the sensible world, including accidental composites, the results of decay, and evils.