The present volume is the ‘successor’ to The Cambridge Companion to Plotinus (1996). Over the last twenty-five years, there has been an enormous increase in published work on Plotinus and on late ancient Platonism generally. In addition, many scholars who had not even begun their careers twenty-five years ago are now working intensely in this area. This fact is reflected in the list of authors of this volume, none of whom appeared in the previous work and most of whom had not yet even begun their careers when the original Companion appeared.1

Nature for Plotinus is near the limit of intelligibility in the hierarchical universe. It is the lowest part of the soul of the cosmos. Hence, all problems in cosmology and biology, prior to their solution, need to be situated within the framework of the ultimate metaphysical explanatory principles of the One, Intellect and Soul. This chapter explores the sense in which Plotinus is and is not receptive of panpsychism, the contemporary philosophical view according to which mentality or consciousness is ubiquitous in the world. Plotinus argues for the idea that nature contemplates which seems, perhaps surprisingly, compatible with the radically anti-Platonic naturalism of panpsychists.

At first glance, Plotinus’ arguments for the immortality of the human soul, principally in Ennead IV 7 (2), constitute a straightforward defense of Plato against Peripatetic and Stoic attacks. And yet, his close reading of his predecessors, especially Aristotle and Alexander of Aphrodisias, led him to confront the following deep problem. The best arguments for immortality rest upon the immateriality of intellect and hence its immunity from destruction along with the body. But, following Aristotle, Plotinus maintains that the nature of intellection is such that the contents of the objects of intellection both identify the agent of intellection and further will be identical for every disembodied intellect. For this reason, it is not clear what it would mean to insist on the personal immortality of anyone. Without personal immortality, though, the ethical dimension of Platonism is, for Plotinus, severely undermined. In the light of this difficulty Plotinus developed an apparently original doctrine that was repudiated by virtually all his successors. He argued that there are Forms of individuals, that is, of individual intellects, and that, since they are eternal Forms, they are ‘undescended’. He argued that the personal identity of any human soul is found paradigmatically in an undescended intellect.

The distinctive features of Plato’s philosophical system are examined, especially his rejection of naturalistic philosophic and scientific approaches and his postulation of an absolutely simple first principle. The Platonists after Plato are then considered, including Aristotle, Alcinous, Numenius, Plotinus, Iamblichus, Proclus. Platonism is conceived as a collaborative project that developed over against opposition – such as Stoicism and, in late antiquity, Christianity – as well through internal debates among its rival schools. The chapter concludes with a discussion of Platonism’s encounter with Christianity after the Edict of Milan.