In his Commentary on Plato’s Timaeus, the fourth-century exegete Calcidius makes ample use of musical theory and its kinship with the related sciences arithmetic, geometry and astronomy. Musical theory impacts upon the metaphysical, physical and ethical aspects in his account of the composition of the cosmic soul. Calcidius draws upon the soul’s musical make-up to show how it translates into the arrangement of the heavenly bodies, the relationships between the immortal and mortal creatures in the cosmos, and the tripartite human soul. Emphasizing the overall significance of harmonics for his exegesis, Calcidius, in fact, likens the creator god to a musician who composed the All as a well-tuned symphony. I shall discuss these aspects of his exegesis by placing them, initially, into the context of his sources, thereafter focusing on more idiosyncratic aspects: Calcidius’ referencing of musical composition for the question of the soul’s (un-)createdness, the relationship he establishes between harmonics and his demonology, and his view on human psychological conditions such as anger and passion. These conditions, according to Calcidius, are not merely a consequence of the human soul’s association with the body, but psychological manifestations of its natural make-up, which is determined by numeric-musical proportions.

This paper explores Platonic and Aristotelian thought on multiplicity, forms, and matter, and considers the relationship between Abrahamic and pagan understandings of the order of divine creation.

The author of De mundo offers his outline of geography in the second part of Chapter 3. In this contribution, we look at the details of the author’s account and analyse it in the context of the historical development of ancient geographic ideas. There is a number of indications that the text can be dated to later Hellenistic times: the author’s view on the insularity of the inhabited world, on the nature and role of the ocean and its connection with the Caspian/Hyrcanian Sea, on the borders between the continents and on the calculation of the dimensions of the inhabited world (oikoumenē). We argue that the author might have been influenced by the treatises on the ocean as a literary model for this section of De mundo. We know that authors such as Pytheas of Massalia, Posidonius of Apamea and Athenodorus of Tharsus wrote works under the title On the Ocean, which survive only in scarce fragments. The information we can extract from De mundo in this respect is, therefore, invaluable for a reconstruction of the content, circulation and reception of this sub-genre of geographic literature in the last decades of Hellenism.

In his commentary on Nicomachus’ Introduction to Arithmetic, John Philoponus explains the role that mathematics, and hence harmonics, play in Platonic philosophy, as redefined by the Neoplatonists. There are two main issues regarding harmonics. The first issue: harmonics is one of the mathematical sciences that lead to the knowledge of divine and absolutely immaterial entities; but harmonics also concerns other mathematical disciplines, because there is an astronomical harmony, that is, the harmony of the revolution of the stars, and there is a geometric harmony, that is, the cube, one of the Platonic solids that are the constitutive elements of the physical world as a geometric model of equality. The second issue: there exists a harmonic proportion, already known to the Pythagoreans, Plato and Aristotle. Both these aspects in Philoponus’ study of harmonics have a common denominator, namely the fact that, as Plato teaches in the Timaeus, the universe, its soul and human souls have a numerical structure based on the relationship between two principles, that is, equality and inequality. But harmonics is precisely the mathematical science of relationship. Therefore, harmonics has a privileged place in the Neoplatonic philosophical system, as Philoponus’ commentary worthily testifies.

This chapter frames the complex and contested concept of Christian Platonism explicated throughout this volume. Here, it is introduced as an object of theological and philosophical contention, the subject of historical and conceptual communication, and a theme of compulsory knowledge for the student of intellectual history.

The notion of Platonic Forms as divine thoughts was critical to the theistic interpretation of Plato’s philosophy. This chapter considers the origins and development of the theory of divine ideas. The chapter begins by examining the evidence for this theory in the Old Academy, including Speusippus, Xenocrates and Aristotle. The notion is then traced among subsequent Platonists, including Antiochus of Ascalon, Eudorus of Alexandria, Alcinous, and the Jewish philosopher Philo of Alexandria. The reception of the theory of divine ideas in Christianity concludes the chapter, with reference to Origen of Alexandria and Maximus the Confessor.

Christian Platonism is a catch-all phrase. It recognizes that Plato and his successors, including the whole of ancient pagan thought, formed part of the complex background to the emergence of a new religion. Both pagans and Christians were mutually transformed by their prolonged encounter on many issues, but especially on the questions of creation, desire, and return. The chapter begins with Judaeo-Christian influence upon major features of the Platonic tradition and then articulates a hidden conversation that lies behind Christian thinking about the Trinity, the structure of reality, and the creation of the human being.

The last part of Chapter 2 and the first part of Chapter 3 of De mundo (392a31–393a8) describe the cosmic layers further below the sphere of the moon, leading down to the very centre of the universe. This section provides a brief overview of the sublunary layers of the four elements (fire, air, water and earth), some of which will be discussed in more detail later in the text. The two main theses that constitute the reasoning behind this section are (i) continuity throughout the entire cosmos and (ii) the great variety of phenomena and processes within the sublunary domain. The layers are organised from the most active one at the top down to the most passive one at the centre of the universe. The continuity among the layers is demonstrated on each and every level. There is, however, no suggestion that each lower, less active substance gains all its characteristics from the more active substance above. For our author’s purpose it is sufficient to demonstrate that there is some relation, some communication among the layers which can later be used by the divine dunamis permeating the entire cosmos. The final part of the present section concerns the claim that the continents are large islands surrounded by an ocean.

This chapter explores the protean character of Christian Platonism in the Romantic Age. If the Enlightenment was frequently shaped by a critique of dogma, tradition and superstition, the Romantics were concerned with the loss of culture, the exaltation of abstract reason, and a longing for the transcendent. Platonism offered a means for revitalizing Christianity, caught between the cultured despisers of religion in the Enlightenment, and the annexation of creation to the mechanistic thought of the emergent natural sciences.

This essay treats of the (Neo)platonic influences in the thought of Thomas Aquinas, in particular the notion of participation. It describes Aquinas’ doctrine of participation in being as developed from his principal Neoplatonic sources, to wit, Boethius’ De hebdomadibus, Dionysius’ De divinis nominibus, and the Liber de causis. It argues that the doctrine of creation in terms of participation the Christian conditions of creation.

Christian Platonism has the capacity to serve as a resource for addressing the present-day environmental crisis. Drawing upon a diverse range of thinkers, including Augustine, Aquinas, Hildegard, Traherne, Coleridge, and Novalis, the chapter illustrates how the tradition envisions a non-anthropocentric conceptualisation of nature.