Ennead I.6 is probably the best known and most influential treatise of Plotinus, especially for Renaissance artists and thinkers. Although the title may suggest a work on aesthetics and thus of limited focus, this is far from the case. For it quickly becomes apparent that Plotinus' main interest is in transcendent beauty, which he identifies with the Good, the goal of all philosophical endeavor in the Platonist's search to assimilate himself with the divine. The treatise is at once a philosophical search for the nature of the divine and at the same time an encouragement to the individual to aspire to this goal by taking his start from the beauty which is experienced in this world; for it is an image of transcendent beauty. This upward movement of the treatise reflects throughout the speech of Socrates in Plato's Symposium in which he recounts the exhortation of the priestess Diotima to ascend from earthly to transcendent beauty, which for Plotinus is identified with the divine.

Platonists beginning in the Old Academy itself and up to and including Plotinus struggled to understand and articulate the relation between Plato's Demiurge and the Living Animal which served as the model for creation. The central question is whether "e;contents"e; of the Living Animal, the Forms, are internal to the mind of the Demiurge or external and independent. For Plotinus, the solution depends heavily on how the Intellect that is the Demiurge and the Forms or intelligibles are to be understood in relation to the first principle of all, the One or the Good. The treatise V.5 [32] sets out the case for the internality of Forms and argues for the necessary existence of an absolutely simple and transcendent first principle of all, the One or the Good. Not only Intellect and the Forms, but everything else depends on this principle for their being.

Filling the void in the current scholarship, Giannis Stamatellos provides the first book-length study of the Presocratic influences in Plotinus' Enneads. Widely regarded as the founder of Neoplatonism, Plotinus (204–270 AD) assimilated eight centuries of Greek thought into his work. In this book Stamatellos focuses on eminent Presocratic thinkers who are significant in Plotinus' thought, including Heraclitus, Parmenides, Empedocles, Anaxagoras, the early Pythagoreans, and the early Atomists. The Presocratic references found in the Enneads are studied in connection with Plotinus' fundamental theories of the One and the unity of being, intellect and the structure of the intelligible world, the nature of eternity and time, the formation of the material world, and the nature of the ensouled body. Stamatellos concludes that, contrary to modern scholarship's dismissal of Presocratic influence in the Enneads, Presocratic philosophy is in fact an important source for Plotinus, which he recognized as valuable in its own right and adapted for key topics in his thought.

Aristotle and Plotinus set the horizon of inquiry—thinking is thinking on thinking. Discussion of mind, meaning, and subjectivity begins with the question, How is thinking on thinking different from the kind of thinking with which we are familiar? The answer is that ‘thinking on thinking’ is about the presuppositions, concepts, and problems that generate questions in ancient and modern metaphysics, epistemology, aesthetics, philosophy of mind, and philosophy of language. Topics examined include the nature of intentionality and meaning, identity and relation, mind and consciousness, self-identity and subjectivity—which lead into discussions concerning other minds, the limits of thought and language, and the emergence of aesthetics of the self. The effects of ‘thinking on thinking’ are mapped, particularly in parsing problems in ancient, modern analytic, and phenomenological thought, with advocacy of its importance in the present age.

Ennead IV.7 is a very early treatise (second according to Porphyry's chronological table), and unlike the many treatises devoted to attempts at untangling various issues Plotinus found problematic in Plato's thinking, this one presents the teachings of the other main schools current in Plotinus' day: the Stoics, Epicureans, Pythagoreans, and Peripatetics, all of whom presented soul as something material or as contingent upon material soul, and so as being neither truly immortal nor imperishable. It includes observations on many mainly Stoic doctrines on perception, memory, sensation, thought, virtue, powers of material bodies, mixture and reproduction (Chapters 1-83); on Pythagorean attunement (84); and on Peripatetic entelechy (85). In Chapters 9-10 Plotinus presents, in broad terms, Plato's doctrines on soul's immortality-mainly that of the individual soul, but a fortiori that of the soul of the cosmos. These chapters offer some of Plotinus' most powerful prose. He is not concerned to prove the soul's immortality-that was an uncontroversial tenet of Platonism, to be taken for granted. In this treatise Plotinus is laying down the indisputable foundations for his later writings.

For Plotinus, the nature and status of the human soul is one of the central problems of philosophy. Ennead IV.3-4.29 constitutes his most penetrating enquiry into this topic, addressing the issues of the relation of the individual soul to the World Soul, the descent of the soul into body, its relations with that body, problems of personal identity and the nature of memory, sense perception, and the true seat of the emotions -many of which still have a resonance today. The treatise is an excellent example of Plotinus' distinctive method of enquiry: not dogmatic (though he is no sceptic), but worrying away at questions until he has uncovered their complexities to the best of his ability. Such a work requires detailed commentary, such as is provided here, to tease out fully the fascinating convolutions of his thought.

Ennead VI.4-5, originally written as a single treatise, contains Plotinus' most general and sustained exposition of the relationship between the intelligible and the sensible realms, addressing and coalescing two central issues in Platonism: the nature of the soul-body relationship and the nature of participation. Its main question is, How can soul animate bodies without sharing their extension? The treatise seems to have had considerable impact: it is much reflected in Porphyry's important work, Sententiae, and the doctrine of reception according to the capacity of the recipient, for which this treatise is the main source, resonated in medieval thinkers.

This book represents the first ever systematic philosophical study of Marsilio Ficino’s Commentary on Plotinus’ ‘Enneads’ (first published in Florence, 1492), this work of Ficino being arguably as definitive for the Florentine thinker’s later work as the Platonic Theology was for his earlier. Publication of the present study uniquely illuminates the extent to which Plotinus had always been the crucial influence over Ficino’s revolutionary projects of introducing Platonic thought based on original Greek sources to western Europe, correcting certain features of late medieval and Renaissance Aristotelianism, and laying the foundations of a new Christian Platonism. The study can be read both as an independent introduction to Ficino’s later philosophy and as the complement to the first modern edition and translation of the Commentary on the 'Enneads' itself also by Stephen Gersh (I Tatti Renaissance Library, 2017-).

The term dunamis (potentiality) entered into the philosophical vocabulary with Plato, but it was with Aristotle that it acquired, together with energeia (actuality), the strong technical meaning that the two terms have maintained, with variations, throughout subsequent philosophical tradition. The significance of the notions of actuality and potentiality in Plotinus' thought can hardly be overstated. Throughout the Enneads, they are crucial to understanding the specific causality of intelligible realities and the relation of participation between intelligible and sensible realms. In Ennead II.5, Plotinus for the first time provides a systematic clarification of his peculiar use of these terms, through a sustained revision of Aristotle's own elaboration of the topic and of his terminology. The treatise discusses the different meanings of potentiality and actuality as well as the way each of them applies or does not apply to the sensible realm, to the intelligible realm, and to matter.