At their first meeting, Porphyry took Plotinus for ‘a complete fool’ and a sophist. This reaction was by no means exceptional.1 The leading Platonists of the time, most notably Longinus, misclassified Plotinus as a representative of an Oriental, Pythagoreanizing version of Platonism.2 Admittedly, it was not easy to understand the novelty of his views. At stake in the discussions with Porphyry and Longinus was the claim that the intelligibles are not outside the Intellect. Marginal as it might appear at first sight, Plotinus’ thesis actually paved the way to a new interpretation of Plato’s Forms, the kernel for any Platonist system. After an intense exchange, Porphyry ‘finally managed to understand what he was saying’,3 wrote a retraction, and became one of his most faithful pupils for the years to come. Most of the other Platonists, however, continued to endorse their traditional interpretation. But in the meantime, the history of ancient Platonism had entered a new phase.

The concept of number is treated at some length in Ennead 6.6, though it is less conspicuous in the rest of the Enneads. This may explain why it does not usually make the headlines of Plotinus’ metaphysics and epistemology – the focus of this part of the Companion – nor of their concomitant scholarship.1 The specialized studies of the concept of number in Neoplatonism in the last twenty years, however, have revealed the essential role of number in the Neoplatonic model of the universe.2 This chapter demonstrates that, below each headline in the Enneads, number writes the story.

Bad things happen in an imperfect world. This, and in particular the fact that they happen to our souls, was a matter of great concern for Plotinus. Near the end of his life, when he was already severely ill, Plotinus wrote a treatise On What Evils Are and Where They Come From (1.8 [51]).1 The text picks up themes and arguments discussed in several other works and will serve as the basis for our discussion of Plotinus’ views on badness. In his view, matter is primary evil and the cause for badness in souls and bodies.

Plotinus has two treatises on the central notions of ancient ethics, named by Porphyry On Virtues (peri aretôn) and On Happiness (peri eudaimonias). Both are found in Ennead 1 but they are not chronologically related. The study on virtues (Enn. 1.2) belongs to the earlier half of the treatises (no. 19) and was written between 253 and 264, while the treatise on happiness (Enn. 1.4) dates from the last year and a half in Plotinus’ life. Scholars have debated about whether Plotinus’ reflections on virtue and happiness amount to a consistent ethics that has something to offer for everyday life.1 I shall return to this question in the concluding section after considering the two treatises. It can be noted already that Porphyry’s title On Virtues (peri aretôn)2 could lead us to expect a comprehensive and practical account of virtue in Enn. 1.2 but no detailed guidelines are given for particular situations. This might suggest that ethics is an entirely theoretical affair for Plotinus. However, Plotinus’ focus is narrower, and it would be premature to exclude practical concerns for a Plotinian virtuous person because of the scope of the treatise.

An enduring interest in categories (katēgoriai),1 and in Aristotle’s Categories in particular, has led readers since antiquity to study the treatise which Porphyry entitled On the Genera of Being (6.1–3).2 Ancient and modern readers broadly agree that: (1) Plotinus understands his own subject matter to be ‘the kinds of things that exist’ (peri tōn genōn tou ontos); (2) the treatise displays the result of a deep and substantial engagement with Aristotle’s Categories; and (3) Plotinus raises important and substantive puzzles (aporiai) about what is said in the Categories.3 Beyond this, plausible interpretations diverge. On one view, Plotinus deploys the resources of earlier Platonist critics to challenge the Categories’ ontological prioritization of particular substance, especially as it is treated by earlier Aristotelian commentators.4 On an alternative reading, Plotinus ‘purifies’ Aristotelian ontology in order to sketch a new taxonomy of the sensible world, complementing his own account of the intelligible world and clearing a trail for Porphyry’s integration of Aristotle into a new Platonist curriculum.5

PEQ: Should we retain the decimal numbering of headings according to chapter number?

It can be difficult to get a handle on Plotinus’ conception of Nature (phusis), not least because of the numerous other connections in which Plotinus employs the Greek term phusis.1 Let us put the other uses of the term aside for now and focus on what I shall henceforth refer to as ‘Universal Nature’ or simply ‘Nature’.2 Universal Nature, for Plotinus, is no mere abstraction but a determinate entity that is causally efficacious in the sensible world in a number of ways.

The Greek word empsukhos (‘ensouled’) was used in ordinary language to describe something as alive.1 Philosophers from all major schools specified this linguistically marked connection between soul and life by postulating or arguing that the soul is the principle of life.2 The soul can be understood to be so in three ways. All life-constituting activities of a living being are activities of the soul, or they are activities of the composite of body and soul, or some are activities of the soul and others of the composite. Plotinus defends the first option.3

With Plotinus, Neoplatonism was inaugurated with the positing of a radical transcendence: the first principle, the One, or the Good,1 is beyond the essence, epekeina tēs ousias. In book 6 of the Republic, Plato already designated the Good as beyond essence, which it surpasses in seniority and in power, ‘epekeina tēs ousias presbeiai kai dunamei huperekhontos’ (509b9–10), but whereas in Plato this formula is found only once, and its interpretation is, moreover, disputed,2 it is recurrent and systematized in Plotinus.3 It also allows a series of variations; beyond essence, the One-Good is also ‘beyond thought’, ‘beyond knowledge’, ‘beyond life’, and, again, ‘beyond act’.4

Knowledge in Plotinus is a complex yet unified phenomenon. His most general term for it, gnōsis (‘cognition’), covers a broad range of phenomena from sense-perception (aisthēsis) via discursive reasoning (dianoia) to intuitive intellectual insight (noēsis).1 The general framework of his epistemology is unambiguously Platonic. Plotinus shares Plato’s conviction, prominently voiced in the Timaeus, that only unchanging intelligible Being admits of real understanding, whereas perception of sensibles only yields opinion or belief.