He made another attack on Platonism in the didactic work περὶ ἰδεῶν, (Fragm. 185 seq.), contending that the Platonic arguments prove not forms (ἰδέαι) but only things common (τὰ κσινά). Here, according to Alexander the commentator, he first brought against Plato the argument of “the third man” (ὸ τρίτος ἄνθρωπος); that, if there is the form, one man beyond many men, there will be a third man predicated of both man and men, and a fourth predicated of all three, and so on to infinity (Fragm. 188). Here, too, he examined the hypothesis of Eudoxus that things are caused by mixture of forms, a hypothesis which formed a kind of transition to his own later views, but failed to satisfy him on account of its difficulties. Lastly, in the didactic work περὶ τἀγαθοῦ (Fragm. 27 seq.), containing his report of Plato’s lectures on the Good, he was dealing with the same mathematical metaphysics which in his dialogue on Philosophy he criticized for converting forms into formal numbers. Aristoxenus, at the beginning of the second book of the Harmonics, gives a graphic account of the astonishment caused by these lectures of Plato, and of their effect on the lectures of Aristotle. In contending, as Aristotle’s pupil, that a teacher should begin by proposing his subject, he tells us how Aristotle used to relate that most of Plato’s hearers came expecting to get something about human goods and happiness, but that when the discourses turned out to be all about mathematics, with the conclusion that good is one, it appeared to them a paradox, which some despised and others condemned. The reason, he adds, was that they were not informed by Plato beforehand; and for this very reason, Aristotle, as he told Aristoxenus himself, used to prepare his hearers by informing them of the nature of the subject. From this rare personal reminiscence we see at a glance that the mind of Plato and the mind of Aristotle were so different, that their philosophies must diverge; the one towards the supernatural, the abstract, the discursive, and the other towards the natural, the substantial, the scientific.
Aristotle then even in the second period of his life, while Plato was still alive, began to differ from him in metaphysics. He rejected the Platonic hypothesis of forms, and affirmed that they are not separate but common, without however as yet having advanced to a constructive metaphysics of his own; while at the same time, after having at first adopted his master’s dialectical treatment of metaphysical problems, he soon passed from dialogues to didactic works, which had the result of separating metaphysics from dialectic. The all-important consequence of this first departure from Platonism was that Aristotle became and remained primarily a metaphysician. After Plato’s death, coming to his third period he made a further departure from Platonism in his didactic works on politics and rhetoric, written in connexion with Alexander and Theodectes. Those on politics (Fragm. 646-648) were designed to instruct Alexander on monarchy and on colonization; and in them Aristotle agreed with Plato in assigning a moral object to the state, but departed from him by saying that a king need not be a philosopher, as Plato had said in the Republic, but does need to listen to philosophers. Still more marked was his departure from Plato as regards rhetoric. Plato in the Gorgias, (501 A) had contended that rhetoric is not an art but an empirical practice (τριβὴ καὶ ἐμπειρία); Aristotle in the Gryllus (Fragm. 68-69), written in his second period, took according to Quintilian a similar view. But in his third period, in the Theodectea (Fragm. 125 seq.), rhetoric is treated as an art, and is laid out somewhat in the manner of his later Art of Rhetoric; while he also showed his interest in the subject by writing a history of other arts of rhetoric called τεχνῶν συναγωγή (Fragm. 136 seq.). Further, in treating rhetoric as an art in the Theodectea he was forced into a conclusion, which carried him far beyond Plato’s rigid notions of proof and of passion: he concluded that it is the work of an orator to use persuasion, and to arouse the passions (τὸ τὰ πάθη διαγεῖραι), e.g. anger and pity (ib. 133-134). Nor could he treat poetry as he is said to have done without the same result.
On the whole then, in his early dialectical and didactic writings, of which mere fragments remain, Aristotle had already diverged from Plato, and first of all in metaphysics. During his master’s life, in the second period of his own life, he protested against the Platonic hypothesis of forms, formal numbers and the one as the good, and tended to separate metaphysics from dialectic by beginning to pass from dialogues to didactic works. After his master’s death, in the third period of his own life, and during his connexion with Alexander, but before the final construction of his philosophy into a system, he was tending to write more and more in the didactic style; to separate from dialectic, not only metaphysics, but also politics, rhetoric and poetry; to admit by the side of philosophy the arts of persuasive language; to think it part of their legitimate work to rouse the passions; and in all these ways to depart from the ascetic rigidity of the philosophy of Plato, so as to prepare for the tolerant spirit of his own, and especially for his ethical doctrine that virtue consists not in suppressing but in moderating almost all human passions. In both periods, too, as we shall find in the sequel, he was already occupied in composing some of the extant writings which were afterwards to form parts of his final philosophical system. But as yet he had given no sign of system, and—what is surprising—no trace of logic. Aristotle was primarily a metaphysician against Plato; a metaphysician before he was a logician; a metaphysician who made what he called primary philosophy (πρώτη φιλοσοφία) the starting-point of his philosophical development, and ultimately of his philosophical system.
III. Composition of his Extant Works
The system which was taught by Aristotle at Athens in the fourth period of his life, and which is now known as the Aristotelian philosophy, is contained not in fragments but in extant books. It will be best then to give at once a list of these extant works, following the traditional order in which they have long been arranged, and marking with a dagger (†) those which are now usually considered not to be genuine, though not always with sufficient reason.
A. Logical
1. Κατηγορίαι: Categoriae: On simple expressions signifying different kinds of things and capable of predication [probably an early work of Aristotle, accepting species and genera as “secondary substances” in deference to Plato’s teaching].
2. περὶ Έρμηνείας: De interpretatione: On language as expression of mind, and especially on the enunciation or assertion (ἀπόφανσις, ἀποφαντικὸς λόγος) [rejected by Andronicus according to Alexander; but probably an early work of Aristotle, based on Plato’s analysis of the sentence into noun and verb].
3. Άναλυτικὰ πρότερα: Analytica Priora, On syllogism, with a view to demonstration.
4. Άναλυτικὰ ὔστερα: Analytica Posteriora: On demonstration, or demonstrative or scientific syllogism (ἀπόδειξις, ἀποδεικτικὸς ἢ ἐπιστημονικὸς συλλογισμός).