The works of Plato are at the heart of the western philosophical tradition. His theory of forms or ideas is the focus of his philosophy. Aristotle, Plato’s greatest pupil, wrote a small treatise, On Ideas, in which he examines and criticizes various arguments for the existence of forms. The treatise survives in substantial fragmentary form in the commentary of Alexander of Aphrodisias on Aristotle’s Metaphysics. Owing both to the author and the subject of the work, On Ideas is arguably an immensely important work in the history of ancient philosophy. Surprisingly enough, however, it has not until recently received a great deal of sophisticated philosophical attention. In part, this is because those who have written extensively about On Ideas were otherwise motivated.
For example, Léon Robin’s ground breaking La Théorie platonicienne des idées et des nombres d’après Aristote (1908) was an attempt to reconstruct Plato’s theory exclusively from the Aristotelian testimony. But in the case of On Ideas, Aristotle cites Platonic arguments in highly elliptical form. It is not useful or even possible to interpret these arguments apart from a meticulous examination of their basis in the dialogues.
Harold Cherniss in his enormously learned Aristotle’s Criticism of Plato and the Academy (1944) had a different agenda. Cherniss set out to prove that Aristotle willfully misinterpreted Plato in almost every important matter and misassigned positions to him that in fact were those of Plato’s successors. This thesis has not met with wide acceptance. In the case of On Ideas, it meant that Cherniss treated Aristotle’s arguments as captious and even obtuse and as not of sufficient interest to warrant the consideration of Plato or a committed Platonist. This meant also that there was no point in wondering whether Plato’s later dialogues might indicate a revision to the theory of forms in the light of Aristotle’s criticisms. No such revision was necessary.
A much more sophisticated level of philosophical analysis was achieved in the works of the late G.E.L. Owen who in the 1950s and 60s wrote a number of incisive and influential articles exploring parts of On Ideas. Owen was adamantly opposed to the approach of Cherniss. But the trivialization of Aristotle’s thought practiced by Cherniss was mirrored by a somewhat similar approach to Plato’s thought by Owen. He believed that Aristotle’s arguments against Plato were not just sound but obviously so and that on no conceivable interpretation could the theory of forms be successfully defended. According to Owen, Aristotle’s demolition of the theory of forms was recognized by Plato himself in the Parmenides after which Plato abandoned the theory. There was no need to explore in depth the putative subtleties of such a theory. What this meant for the treatment of On Ideas is that one could just settle for the simplest interpretation of the arguments for forms that left them open to straightforward refutation.
Gail Fine’s treatment of On Ideas is far superior to any of the above mentioned works. Indeed, it is the first full length philosophical monograph on the subject in English. It is notable and practically unique in taking seriously both the theory of forms and Aristotle’s criticism of that theory. Fine thinks she can interpret the arguments in a way that is rooted firmly in the Platonic texts and that makes them philosophically interesting. She thinks that she can show that Aristotle’s criticism are powerful and subtle and fair. She also thinks that Plato is not without resources to respond to these arguments whether by rejecting certain of their implicit premises or by altering the theory of forms in defensible ways. According to Fine, such responses by Plato would by no means signal the end of the debate. For an Aristotelian rejoinder would reveal fundamental differences in matters of principle between the two protagonists. In short, Fine’s book is a sustained argument for the thesis that On Ideas is a work that pays rich dividends to anyone willing to devote serious and unprejudiced attention to it.
Fine prints Harlfinger’s text of the fragments of On Ideas contained in Alexander’s commentary along with a literal translation. In four foundational chapters she discusses a wide ranging number of issues relevant to a close study of On Ideas. These include the philosophical issue of the theory of forms as a theory of universals, the development of a mature theory of forms in the middle dialogues from its earlier stage as a Socratic theory, Aristotle’s criticisms of Plato’s theory in his other works, and the authenticity and purpose of the On Ideas itself. In general, these chapters are models of clarity and mature reflection. Those who are familiar with Fine’s many articles on the metaphysics of Plato and Aristotle will find in these chapters a concise and forceful statement of her views on these matters. Particularly helpful is her sustained and nuanced argument against the interpretation of the theory of forms as primarily a semantical theory (24, 50). These chapters also contain a careful discussion of how Plato argues for the existence of forms in the middle dialogues, though here I would take issue with Fine on several important details. Fine is right and importantly so when she claims that forms are explanatory entities. But it seems to me a mistake to describe a form as a ‘determinable property’ (62), for she thus undermines the priority and hence the explanatory role of the forms. A paradigm as such cannot be a determin able. I think it is also a mistake to hold that Plato and Socrates believe that the sensible world is knowable or that through knowledge of forms one can thereby have knowledge of sensibles (59, 64). Such a claim might make Plato’s theory of forms more palatable to contemporary philosophers, but it does not I think accurately represent Plato’s true view.
The heart of this book is a detailed analysis of the five arguments for forms developed in the On Ideas and Aristotle’s reasons for rejecting these. Fine has a most elegant hypothesis for understanding the strategy behind these five arguments that are apparently only loosely connected (201-2). Platonists have two types of arguments for forms: the less accurate and the more accurate. The former (the so-called ‘one over many argument’, the object of thought argument, and the argument from the sciences) are invalid because their conclusion does not follow from their premises. But they would be valid (and sound) if instead of concluding that forms exist, they concluded that Aristotelian universals exist. The latter (the argument from relatives and the accurate version of the ‘one over many’ argument) are valid arguments for forms but they cannot be sound because they have intolerable consequences. That is, one leads to positing forms that the Platonists themselves do not want and one leads to a vicious infinite regress.
One might question whether when Aristotle speaks of a ‘more accurate’ ( akribesteron) argument he just means ‘valid’ argument. But perhaps this is part of what he means. And in any case, Fine’s way of understanding Aristotle’s strategy is fruitful and provocative. It opens up three lines of argument for Plato in reply: (1) show that in fact the invalid arguments are valid arguments for forms if additional premises are added or premises differently construed; (2) show how the unwanted forms can be otherwise excluded non-arbitrarily; (3) show how the vicious infinite regress can be avoided without compromising other claims that comprise the theory of forms. Fine spends a good deal more time on (2) and (3) than on (1). In particular, she has left unexplored many things that could be said about Plato’s reasons for separating of forms, which is of course the crux of the dispute between the Platonists and the Aristotelians.
The separation or independent existence of forms is for Plato logically connected to the imperfection of the sensible world. He holds that a recognition of this imperfection commits one to separation, roughly as a recognition of counterfeit currency commits one to the existence of the real thing. If the form is perfectly that which its instances are imperfectly, must we hold that, say, the form of beauty is beautiful, the form of largeness is large, and the form of man is a man? Fine recognizes the absurdity of one obvious interpretation of this claim. For example, just how large are we to suppose the form of largeness is? And if the form of man is a man, is it male or female? But Fine is nevertheless convinced that Plato is committed to self-predication in some sense. Her interpretation is that to say that a form F is f means that the form explains why anything else is f. The form is f ‘in a sui generis way, simply in virtue of its explanatory role (62)’. Evidently, Fine understands this claim in a way such that it is distinct from another traditional interpretation according to which the form is identitatively that which its participants are predicatively (cf. 272, n75). I do not see, though, how the form explains anything if it is not identitatively that which its name names. What Fine calls ‘broad self-predication’ seems therefore rather unhelpful as an interpretation. This question is of considerable importance for understanding how if at all Plato can reply to the arguments which Aristotle says lead to a vicious infinite regress.
The close logical connection of self-predication, separation, and the imperfection of the sensible world means that the interpretation of one of these facets of the theory of forms will cause some readjustment in the interpretation of the others. This is especially true for someone with Fine’s considerable logical acumen. Those who, like myself, are not convinced by her interpretation of self-predication, will, not surprisingly, have further doubts regarding at least the details of her interpretation of the other facets of the theory. Nevertheless, her book is an excellent contribution to the subject. It deserves the most careful attention of anyone interested in Plato’s metaphysics. It is also a splendid example of how analytic philosophy and the history of philosophy can be mutually enriching.