There is something very Aristotelian about the Third Man Argument—including the name. For Aristotle (but not Plato), the most real things are biological specimens, like Man (in the sense of a human being, member of the species Home sapiens). For Plato a non-substantial property like Largeness will do quite well as a Form. Furthermore, Aristotle is a logician—quite literally. He invented the first system of logic in his treatise Prior Analytics. Plato can recognize logical fallacies, but he has no system of logic, nor does anyone else before Aristotle. Aristotle likes to take arguments apart and put them together again; Plato likes to develop analogies like that between the soul and the state in his Republic, and between the soul and the charioteer in the Phaedrus.
Furthermore, Aristotle likes to systemize things: five arguments for the Theory of Forms, five objections corresponding to them. He seems to have first published it in his dialogue On Ideas. Then he reminds us of one of the arguments elaborated in it, the Third Man Argument, in his lectures.[20]
Scholars reasonably dismiss Aristotle from consideration. Gail Fine, in her comprehensive study of Aristotle’s On Ideas, notes that “It is … just chronologically possible (if not especially likely) that the [On Ideas] antedates the Parmenides.” But this possibility is “unconvincing.” Furthermore, “it is unlikely that Plato is referring to ‘our’ Aristotle. For he identifies the Aristotle he mentions as a member of the Thirty …” And “Plato does not generally refer to living philosophers by name.”[21] But, of course, if Plato is alluding to “our” Aristotle, he is not referring to him by his own name, but homonymously, as Aristotle would say, by using someone else’s name. In any case, it is simply false that Plato does not name living persons (whether philosophers or not) in his dialogues.[22]
So Aristotle expounds the Third Man Argument in an early dialogue, then cites it in subsequent works as a knockout blow to Plato’s Theory of Forms. Did he invent the argument as a few scholars have proposed?[23] We cannot be sure. But it would take a thinker of logical acumen and a vested interest in undermining the Forms. Nevertheless, if Aristotle wrote On Ideas before the Parmenides, the dialogue “was written very early in Aristotle’s career, perhaps before he was even 20 years old.” This “seems unlikely given the depth of understanding the [work] reveals about the theory of forms.”[24] If Aristotle did this, he would have to be—what? A genius? The man who evidently developed the first theory of categories while he was in Plato’s Academy? Who invented the first system of formal logic in his early years, virtually ex nihilo? Who put zoology on the path of a science? Who systematized psychology? Who systematized the study of ethics? Who invented the philosophy of science in his early years? Who provided the first extant proofs of the sphericity of the earth? Who established the autonomy of the sciences and initiated programs of scientific research?
In any case, as a member of Plato’s Academy, Aristotle would not have needed to publish his objections to the Theory of Forms to make them known to the school. He could have announced them among the fellows of the Academy, and polished and published his challenges later. Still, he seems to have formulated his objections early, so as to be able to refer to the Third Man Argument by name in his early Sophistical Refutations. But if he had published the work early on (or someone had copied and distributed it without authorization—for publication in the ancient world consisted merely of copying manuscripts longhand),[25] that would give Plato the impetus to reply to it in writing.
If someone else invented the Third Man Argument and the other objections to the Theory of Forms, who was it? Given that many other members of the Academy were devotees of the theory in some version or other, it seems unlikely any other fellow would challenge Plato directly. There were other philosophers who might have raised objections to the theory, but did they have the logical expertise to take the Theory of Forms apart, identify its key premises, and then weaponize it against Plato?
We know that Aristotle had analyzed Plato’s Theory of Forms and distinguished the One Over Many principle as a key premise. He continued to cite the arguments of the On Ideas as part of a panoply of objections to Plato’s Forms forever after the publication of his dialogue. If they were not his own objections, he certainly made them his by his repeated use of them. Perhaps, however, we should invoke Ockham’s Razor and ascribe the objections to their most vocal advocate, as the only thinker who had the acumen, the incentive, the chutzpah, and, within the Academy, the platform to challenge the scholarch.
[20] Aristotle Metaphysics 990b17; 1039a2; 1079a13; On Sophistical Refutations 178b36.
[21] Fine 1993: 39.
[22] E.g., Isocrates, Plato Phaedrus 278e; some Socratics, Apology 33d-34a; Plato, Apology 38b; another set of Socratics, Phaedo 59a-c.
[23] Phillipson 1936; Düring 1956.
[24] Fine 1993: 40.
[25] As Zeno reminds us in Plato’ Parmenides, 128d-e.