This short book by one of the preeminent scholars of Platonism is a collection of six distinct papers (of which three have been published elsewhere) devoted to “the process by which the intellectual speculations pursued by Plato in the (rather informal) institution that he set up in the Academy park on the outskirts of Athens around 387 BCE, and that he presided over until his death forty years later, came to assume the nature of a philosophical system”—in other words, how it is Plato gave rise to Platonism (pg. 1). If Plato “was more concerned with the free exploration of philosophical problems,” conditioned by what Lloyd Gerson has defined by a set of decidedly negative commitments—anti-materialism, anti-mechanism, anti-nominalism, anti-relativism, and anti-skepticism—then Platonism (both the Old and New Academies) emerges as a self-defined school with its own orthodox doctrine and set of heresies (pg. 2).
The first three chapters follow the trail of dogmatic Platonism back to the Old Academy and its first few scholarchs, especially Xenocrates (396/395-314/313 BCE). Chapter One explores whether there is any justification for the later Platonists’ conviction that Plato and the Old Academy offered a coherent dogma. Dillon argues that the later tradition was half right: it was not Plato himself but the Old Academy that initiated this dogmatism. Sextus Empiricus credits Xenocrates with first dividing philosophy into three topics: physics, ethics, and logic. In order to demonstrate how Plato addressed all three topics, Xenocrates needed to assemble a complete and definitive edition of the master’s works, a conjecture which strikes Dillon as “entirely probable” (pg. 11). With such an edition in hand, and facing criticisms from the Peripatetics, Xenocrates and his successor Polemon provided the basis for a body of Platonist dogma, which the later tradition would credit to Plato himself. Dillon concludes by insisting that this early Platonist dogmatism was not a “monolithic orthodoxy” of the sort that Christianity would offer in the centuries to come. It was, rather, a “self-regulating system,” in which there was no centralized authority to determine who was and who was not a proper Platonist (pg. 23). Endless squabbling over details was a sign of one’s commitment to the larger, shared framework.
Chapter Two begins with Plato’s agrapha dogmata or “unwritten doctrines,” especially the alleged two first principles, the One and the Indefinite Dyad. Whether the Indefinite Dyad, often identified with matter, qualifies as a first principle is a matter of some debate among the first generation of Plato’s heirs: Hermodorus insists that “there is only a single first principle,” that is, the One. Plato’s nephew and first successor Speusippus admits them both as “two primary and highest principles.” But both heirs would deny that the second principle is in any sense evil, actively opposed to the One. Rather, the second principle cooperates with the first in order to bring division (diairesis) into the world—division not in the sense of any catastrophic dissension but rather in the sense that every being is defined and differentiated from every other being, and thereby individuated. Xenocrates also emerges as the innovator in another key: according to Plutarch, he places the sublunar world under the dominion of a secondary god, sometimes figured as Hades and other times as Dionysus. We are still centuries away from the elaborate Gnostic myths of the demiurge, but it is a step in that direction. Xenocrates is also said to have entertained the concept of evil or malevolent daemons, which departs dramatically from the discussion of daimones in Plato’s dialogues and perhaps anticipates Christian demonology. Just as with dogmatism, so too with dualism: the trail leads back to Xenocrates.
Chapter Three takes up the question of where the Forms are thought to reside. Do they perhaps reside in the human mind? This seems too subjective for what is supposed to secure reality, and it is also a view explicitly rejected by Parmenides in the eponymous dialogue (132B-C). But what about inside the mind of God? This seems to be the established dogma of Platonism in the 1st c. BCE, evident in Antiochus of Ascalon, Eudorus of Alexandria, and Philo of Alexandria. Once again, though, Dillon traces the path of this idea back to Xenocrates, for whom the first principle was a Monad which is also a Mind (Nous), and, as Dillon remarks, “an intellect must necessarily have thoughts!” (pg. 4). He regards this idea as following from a non-literal or demythologized interpretation of the Timaeus, which we know that Xenocrates and Speusippus offered. Xenocrates identifies the first principle or Monad-Mind with the Demiurge, who in consulting an eternal “paradigm” as he creates the world, is interpreted as consulting the Forms that reside in his own mind. This would seem to be an elegant solution: God the Monad-Mind thinks the eternal Forms eternally, consults them in his capacity as creator, and thinks them into being as a world of particulars. But evidently some worried that a God who did so much thinking, even if thinking his own thoughts, might be riven with duality (thinking vs. thought) and thus not be the supreme principle after all. Dillon credits Plotinus with affirming Xenocrates’ view that the Forms reside in the mind of God, but then demotes that thinking God to second place, decidedly posterior to “the radically unitary status of the first principle,” the One (pg. 49).
Chapter Four pivots to ethics, exploring the implications of Plato’s metaphysical hierarchy for his conception of the telos or goal of human life. The famous phrase from Theaetetus 176B for that telos—“assimilation to God in so far as that is possible”—was understood by Plato, the Old Academy, and even Antiochus of Ascalon as something rather “horizontal”: the goal of human life is to be governed by reason and practiced in the virtues. But later Eudorus of Alexandria (fl. 1st c. BCE) insists on a more “vertical” interpretation of Theaetetus 176B, suggesting that the wise man’s way of life brings order out of disorder, and thus mirrors and perhaps even participates in God’s efforts at creating and maintaining an ordered world out of chaos. In the generation following Eudorus, Plutarch of Chaeronea (c. 45-120 CE) further strengthens the link between the metaphysical hierarchy and the ethical pursuit of “assimilation to God,” and gives greater stress to divine agency in that pursuit. Just a step behind Plutarch we find Alcinous (c. 2nd c. CE) giving an equally vertical interpretation of Theaetetus 176B, but with one significant caveat: the god to whom one is supposed to assimilate is “the god in the heavens” and decidedly not “the god above the heavens.” Once a distinction between primary and secondary gods is introduced, the question arises as to whether assimilation is to the one or to the other, or to both. Alcinous limits our assimilation to the lower, secondary god, in the heavens. But Plotinus will go on to clarify the difference between the first and the second, between the One and Intellect (Nous), and to insist that assimilation can ascend all the way up the metaphysical hierarchy, all the way to the transcendent source.
Chapters Five and Six take us from the Old to the New Academy and beyond. Both chapters explore how Platonists metabolized the skepticism of the New Academy. Chapter Five focuses on Carneades of Cyrene (c. 214-129 BCE), in whom the New Academy is said to culminate. Dillon explores whether and how Carneades’ skepticism can be understood as his attempt to recover the philosophy of Socrates from the dogmatism of the Old Academy. He leans on the work of Vasilis Politis, who regards the interpretation of Socrates as on a spectrum, with “Socrates the Sceptic” at one end, and “Socrates the Visionary” at the other. Politis and Dillon both put Socrates somewhere in the middle, arguing that his elenchic philosophy is in the service of a positive doctrine. Dillon argues that Carneades is “Socratic” insofar as he is also somewhere in this middle ground, balancing a total skeptical suspension (epokhé) with some positive doctrines, and thus settling on a means by which, in the words Myles Burnyeat, he is able to “live his scepticism” (rather than be paralyzed by it). Chapter Six focuses on Plutarch, one of the few later Platonists who are appreciative of the New Academy’s skepticism, especially as it serves his polemics against Stoics and Epicureans. But just as with Carneades, Plutarch understands Socrates’ elenchic philosophy as a means and not an end, a goad to awaken in his interlocutors their reminiscence (anamnesis) of reality. Socrates’ profession of his own ignorance, and his withholding of his own views, is understood as a maieutic means, playing the midwife to the (re)birth of reality in the oblivious soul of another.
The arguments in this short book are the fruits of a long and prolific career, and are by and large convincing. But it is not a book for the uninitiated: although short, it assumes quite a bit of familiarity with the sources and the relevant scholarship. One thing to note, in light of the book’s title, is the choice of a rather striking cover image. It is a famous image from a fourteenth-century Buddhist temple in Thailand: Wat Mahathat in Ayutthaya. The Burmese army sacked the temple in the eighteenth century and decapitated many of the Buddha statues. Somehow a tree grew up and around one of these heads, whose face now peers out amongst the tree’s many roots. The face is supported by the roots, but also nearly strangled: the Buddha’s slight smile and half-open eyes leaves a viewer wondering what this face thinks of its fate, and its future. The reader of The Roots of Platonism, of course, is invited to think of Plato rather than the Buddha, and it becomes hard not to wonder whether Plato might be lost among the tangle of Platonism’s roots. I doubt this is what Dillon intends to mean. But then why then is this image “so apt” (pg. x)? Is the image meant to alarm, as if we run the risk of losing Plato to Platonism? Or is it rather that Dillon imagines Plato welcoming his fate with that same slight smile and half-open eyes? Is Plato being established, or enveloped?
 Lloyd Gerson, From Plato to Platonism (Ithaca: Cornell University Press, 2013).
 Sextus Empiricus, Against the Logicians, I.16; cited on pg. 10
 Simplicius, In Physica, pg. 247, 30ff. = Hermodorus, Fr. 7 Isnardi Parente; cited on pg. 26
 Iamblichus, De Communi Mathematica Scientia 4, pg. 15, 5fff. (Festa), 26; cited on pg. 26
 See Carl Séan O’Brien, The Demiurge in Ancient Thought: Secondary Gods and Divine Mediators (Cambridge: Cambridge University Press, 2015).
 Alcinous, Didaskalikos, ch. 28, 181, 36-45; cited on pg. 59
 Vasilis Politis, The Structure of Inquiry in Plato’s Early Dialogues (Cambridge: Cambridge University Press, 2015), pg. 10.
 Miles Burnyeat, Explorations in Ancient and Modern Philosophy (Cambridge: Cambridge University Press, 2012), Chapter 8, “Can the sceptic live his scepticism?”, pp. 205-235.