253WHAT IS PLATONISM? Journal of the History of Philosophy, vol. 43, no. 3 (2005) 253–276 [253] * Lloyd P. Gerson is Professor of Philosophy at the University of Toronto. What is Platonism? LLOYD P. GERSON* 1 . THE PROBLEM the question posed in the title of this paper is an historical one. I am not, for example, primarily interested in the term ‘Platonism’ as used by modern philosophers to stand for a particular theory under discussion—a theory, which it is typically acknowledged, no one may have actually held.1 I am rather concerned to understand and articulate on an historical basis the core position of that “school” of thought prominent in antiquity from the time of the “founder” up until at least the middle of the 6th century C.E.2 Platonism was unquestionably the dominant philosophical position in the ancient world over a period of more than 800 years. Epicureanism is perhaps the sole major exception to the rule that in the ancient world all philosophers took Platonism as the starting-point for speculation, including those who thought their first task was to refute Platonism. Basically, Platonism set the ancient philosophical agenda. Given this fact, understanding with some precision the nature of Platonism is obviously a desirable thing for the historian of ancient philosophy. One might suppose that the task of determining the nature of Platonism can be handled in a relatively straightforward and perspicuous manner if one stipulates that Platonism is the view or collection of views held by all those who called themselves Platonists or followers of Plato. Thus, we could take a purely phenomonological approach: Platonism is just whatever anyone in the relevant 1 Willard van Orman Quine and Richard Rorty come readily to mind as two prominent philosophers who have used the label ‘Platonism’ as a foil for the development of their own philosophical positions. I am very far from holding that modern uses of the term ‘Platonism’ are unconnected or only uninterestingly connected with the historical reality. Nevertheless, precisely because there is some connection, albeit at times remote, it is would be useful to have a clear grasp of the historical phenomenon before arriving at judgments about either. 2 That Platonism was actually held in some sense to antedate the teachings of Plato is one surprising fact that I shall address below. I am here interested in the Platonism that is, to use the unfortunate pejorative term, ‘pagan.’ So, I shall have nothing to say about, for example, Christian Platonism except by implication and on the assumption that this label indicates one historical variety of Platonism. 254 JOURNAL OF THE HISTORY OF PHILOSOPHY 43:3 JULY 2005 period identifies as Platonism.3 A similar approach could be made in determining who is a Platonist. As a strictly historical method, this is not an unreasonable way to proceed.4 Nevertheless, it have several drawbacks. First, the fact that philosophers did not self-identify as Platonists until sometime in the 2nd century C.E. means that we would have to exclude from our construction of Platonism, on the basis of a technicality, as it were, the contributions of many philosophers who were quite evidently in some sense followers of Plato and of his philosophy. The list of the philosophers thus excluded would be quite impressive. It includes members of the Old Academy such as Speusippus (c. 410– 339 B.C.E.) and Xenocrates (396/5–314/313 B.C.E.) as well as numerous significant figures of what is anachronistically called Middle Platonism such as Antiochus of Ascalon (c. 130–c. 68 B.C.E.) and Numenius (2nd century C.E.). I single out these philosophers from among many others because the remains of their writings—in some cases extensive and in others exiguous—surely have some role to play in giving an historical answer to my question. In this regard, the skeptical philosophers of the New Academy, Arcesilaus (316/315–241/340 B.C.E.), Carneades (214–129/8 B.C.E.), Clitomachus (187/6–110/09 B.C.E.), and Philo of Larissa (158–84 B.C.E.) are especially interesting.5 For...