 Hi, I'm Peter Adamson, and you're listening to the History of Philosophy podcast, brought to you with the support of King's College London and the Leverhulme Trust, online at www.historyoffilosophy.net. Today's episode, The Next Generation, the followers of Plato and Aristotle. As I believe I may have mentioned at some point, this series of podcasts aims to cover the history of philosophy without any gaps. We've just finished Aristotle, and it's right about here that there would normally be a gap. In an undergraduate philosophy course, you might reasonably expect to jump from Aristotle to perhaps Descartes, leaping over about 2,000 years of history in the process. A more enlightened approach might include looking at Thomas Aquinas in the 13th century, still omitting the better part of two millennia. Better still would be to skip only as far as Plotinus or Augustine in late antiquity. Of course it's fair enough to be selective in designing a philosophy curriculum, and to concentrate on the household names. But given that we have the luxury of going at our own pace with these podcasts, I'm not going to skip ahead at all. Rather, I'm going to devote a good number of episodes to the philosophical movements which began already in the lifetime of Aristotle, and which dominated the Hellenistic period. There are some household names here, too. The Stoics, the Epicureans, the Skeptics. But to continue our story with these Hellenistic schools would still be to leave something out. One of the most striking and puzzling features of Hellenistic philosophy is that Plato and Aristotle play a relatively small role. Though the Stoics and others did respond to them, it took a few hundred years for their influence to become dominant. Still, Plato and Aristotle had established schools with physical property to keep them going and groups of disciples to carry on their work. It's this immediate legacy that I want to consider in today's episode, first looking at the so-called Old Academy, Plato's two immediate successors, Spusippus and Seidocrates, not to be confused with the presocratic thinker Xenophanes. Then I'll be checking in at the Lyceum, to see how Aristotle's school got on without Aristotle. Here, the main personality to discuss is Theophrastus. I know what you've all been thinking. Sure, Aristotle shows an impressively encyclopedic range, inquiring into everything from logic to animals to the rules of good poetry, but hey, what about plants? Well, Theophrastus is just the man to fill that particular gap. Before we look at the roots of Aristotelianism with Theophrastus, though, let's look at the brief blossoming of hardcore Platonism in the wake of Plato's death. I've just mentioned that Plato's immediate successors as heads of the academy, Spusippus and Seinocrates, are often referred to under the rubric of the Old Academy. This is in contrast to the so-called New Academy, who came after them. The New Academy took their cue from a rather different Plato than the one who inspired Spusippus and Seinocrates. New academics were skeptics. They were particularly impressed by Plato's early Socratic dialogues, in which Socrates raises philosophical questions, refutes whatever answers are offered, and draws things to a close with an expression of puzzlement. Spusippus and Seinocrates were instead inspired by the Plato whose mathematical, logical, and metaphysical speculations are on display in dialogues like the Timaeus and Sophist. This brand of Platonism would go out of fashion for a few centuries, only to return with a vengeance in the Roman Empire. When I say that the Old Academy took its cue from the more technical dialogues of Plato, I'm actually leaving something out. But then Plato left it out too. It would seem that Spusippus and Seinocrates were trying to develop ideas which had been discussed in Plato's academy, but which either were omitted from the dialogues or were referred to only very obliquely. These ideas are sometimes called by the somewhat histrionic phrase, unwritten doctrines. Since even the most intrepid historian of philosophy can't read unwritten doctrines, we have to rely on indirect sources of information about this aspect of Plato's teaching. This means, above all, relying on Aristotle. He's our main source for some of the ideas Plato apparently didn't see fit to share with us in his dialogues. He's also our main source for the way that Spusippus and Seinocrates carried on those ideas. So it's a bit unfortunate that Aristotle thought the unwritten doctrines were ludicrous and barely worth taking seriously. Imagine Donald Trump trying to explain the principles of Marxism, and you'll get a pretty close idea of Aristotle's trustworthiness as a reporter on this particular topic. The most famous story about Plato's unwritten doctrines, though, is found not in Aristotle, but in later authors beginning with Aristotle's student Aristoxenus, who nonetheless is just reporting what Aristotle told him. At any rate, the story goes that Plato offered to give a public lecture on the topic of the good. An audience turned up, expecting to hear about how to acquire happiness, perhaps by way of wealth, health, and other such goods. Instead, they got a long lecture on mathematics, and went away totally bemused. This rather depressing story suggests that even if Plato had written down his unwritten doctrines, we still might not be able to figure out what he was talking about. But if it has any basis in truth, it shows that Plato believed mathematics to be at the core of philosophy, including what we would think of as ethics, inquiry into the nature of the good. Though we don't find this story about the lecture on the good in Aristotle's own works, we do find him explaining, or at least making fun of, Plato's ideas about numbers and how they relate to his theory of forms. The theory, as Aristotle tells it, is complicated and mysterious. Many Plato scholars are happy to ignore it, preferring the literary riches of the real Plato's dialogues to the off-putting abstractions Aristotle puts in Plato's mouth. Others think they can find traces of the so-called unwritten doctrines in the dialogues. Either way, we can't understand the old academy without saying at least a little bit about this theory, so here goes. Plato seems to have been taking up ideas from the mathematics-obsessed Pythagoreans. He was particularly interested in the production of numbers from two principles, a principle of unity and a principle of multiplicity. Plato apparently called the second principle the great and small. The idea was that you could get numbers by imposing some limit or unity on a continuum. Imagine a musical scale, for instance, remembering that for the Greeks, music and mathematics were intimately related. What you have is a range of sounds, which become musical notes only when certain limits or intervals are imposed. Similarly, numbers would emerge from the interaction of unity and multiplicity. In the old academy, this was sometimes understood in frankly sexual terms. Simplicity is a male principle, multiplicity a female principle, and from their copulation are born the numbers. And you thought Pythagorean metaphysics was dull. Aristotle further tells us that Spusippus and Xenocrates took up these ideas of Plato and tried to work them out in detail. An anecdote about Xenocrates relates that he asked a would-be student whether he knew anything about geometry or astronomy. The aspiring philosopher admitted that he did not. Xenocrates sent him away saying, you give me no handles for philosophy. This is to be put in the same box as the legend about the sign posted outside the academy. Only those who have studied geometry should enter. Whether or not there's any truth in these stories, the successors of Plato certainly agreed with the sentiment. They put forward their Pythagoreanizing version of Platonism in the setting of Plato's academy, whose headship Spusippus inherited upon Plato's death in 347 BC. Spusippus was Plato's nephew, so this was keeping the business in the family. Xenocrates took it over next in 339, supposedly to the annoyance of Aristotle, who in a fit of pique set up the rival Lyceum. Here I should remind you that the academy was named after a grove or park, the Akademos, outside the walls of Athens. Plato seems to have acquired a house near the grove, which was public property. He and his associates would have pursued philosophy both in the pleasant surroundings of the public grove and in the private household. By all accounts, they spent a lot of their time on mathematics. Aristotle is again our source for certain astronomical theories developed in the academy, for instance by Plato's associate Eudoxus, who devised mathematical models of the planetary motions we see in the night sky. In the dialogues, Plato recommends astronomy as a stepping stone towards philosophy, and that was certainly put into practice in the academy. Another favorite activity was classification and division. In an earlier episode, we've already heard the story about Diogenes the Cynic, mocking the academy's definition of man as featherless biped. He turned up with a plucked chicken and said, here is Plato's man. He wasn't the only one who was amused. A comic author named Epikrates depicts academic philosophers sitting around trying to decide whether the pumpkin is a vegetable, a tree, or a kind of grass. In fact, this is a feature of the academy that is written in the dialogues, for instance in the sophist, with its method of collection and division. Plato's successors too wrote treatises on logical method. Spusippus supposedly said that unless you can enumerate all the ways one thing differs from another, you lack knowledge about both things. But like everything else they wrote, these treatises on division and classification are lost. This is why we're dependent on Aristotle's rather tendentious testimony. He mostly focuses on their theory of first principles, which was based on Plato's theory about unity and multiplicity. Aristotle tells us that Spusippus derived a series of further principles from these two basic foundations. For Spusippus, the one, or monad, interacts with multiplicity, the so-called dyad, to generate numbers, and then geometrical figures, like triangles for instance. The soul of the world then builds a physical universe on the basis of these geometrical figures. That sounds pretty weird, but you might remember that Plato's Timaeus does talk about a world soul, and offers a geometrical analysis of the four elements, saying that fire, air, earth and water are made up of atomic shapes formed from triangles. So the weirdness, both written and unwritten, already started with Plato. Aristotle's big complaint about Spusippus is that his system is episodic. In other words, all these levels, the principles of number, the numbers, the figures, and then bodies, seem to be more or less independent, like the layers in a sandwich that threatens to fall apart when you try to eat it. He also presents Spusippus as if he eliminates Plato's forms, and replaces them with numbers. But this is probably a distortion. Rather Spusippus was in some way identifying forms with numbers, or perhaps with the principles that generate numbers. Aristotle isn't much more impressed by Sinocrates, but he does imply that Sinocrates made more of an effort to tie the levels of his system together. Sinocrates again has a monad and dyad as generating first principles. Below this, he envisions three levels of reality, forms, mathematical entities, and the bodies you can actually see. He thinks of the mathematical entities as a kind of middle level, which can tie together the forms and the bodies. Again, he puts the soul at this middle level, and even says that soul itself is a moving number. It brings the motion of life and the structure associated with number. This all sounds pretty abstract, and if you're being ungenerous, not even very philosophical. It suggests that the old academy was taking a good idea way too far, the good idea being the Pythagorean and Platonic conviction that reality has an underlying mathematical structure. But the old academy's ideas had staying power. In particular, the idea that reality derives from a single principle of unity will become fundamental in the Platonism of late antiquity, and from there it will go on to influence religious ideas about God in Judaism, Christianity, and Islam. In those traditions, there was constant debate about whether this single first principle is beyond our understanding, or comprehensible as the first of causes. Spusippus and Xenocrates anticipate this debate. Spusippus is reported to have said that the principle of unity is beyond even goodness and being. In future episodes, we will see that later authors make a similar claim, for a variety of reasons. Spusippus' reason is that since the principle is the source of these things, it cannot partake of them. Xenocrates, by contrast, said the monad was a kind of divine mind, like Aristotle's god perhaps. Maybe he even wanted Plato's forms to be ideas in this godlike intellect. Here then, at the infancy of Platonism, we have one of the most fundamental tensions that will occupy our attention when we reach late ancient and medieval philosophy. Is God, the first principle, so transcendent that He surpasses our concepts and our language? Or is He sort of like us, but better, a mind that can think about everything instead of only a few things at a time? It should also be said that Spusippus and Xenocrates did not spend all their time worrying about numbers and gods. They also had things to say on the subject of ethics. There's a great story about Xenocrates going with Plato and Spusippus to the court of the tyrant Dionysius in Syracuse. You might remember from my episode on Plato's biography that this association turned out badly. On some accounts Plato barely escaped with his life. Supposedly, Dionysius threatened to execute Plato, and the faithful Xenocrates stepped forward and said, only after you cut off my head first. But before these unpleasant scenes everyone had been getting along famously. Clearly if you invite philosophers to your court you need to host a drinking contest, and this is what Dionysius did. Xenocrates drank everyone else under the table and was awarded a gold laurel wreath. Displaying his disdain for material wealth, he left the gold wreath on the head of a statue of Hermes in the city. This disdain for the things valued by most of us is confirmed by the little we know about the ethics of the old academy. It seems that they didn't care much for pleasure. Xenocrates encourages us to look after both the soul and the body, but more especially the soul, which he says is our daimon or guardian spirit. Before him, Spusippus recommends a life in accordance with nature, which is as free as possible from trouble and disturbance. This means steering clear of pleasure as well as pain. As we'll see soon, these ideas of living naturally and achieving a quiet undisturbed existence are commonplace in Hellenistic philosophy, and it's interesting to see them turning up in Plato's immediate successors. Soon we'll see Hellenistic philosophers fighting over the role of pleasure in the good life and pleasure's relation to virtue. This was already a hot topic in the academy. It's not only Spusippus and Xenocrates who raised the issue, but also that astronomical whiz kid Eudoxus. Eudoxus, according to Aristotle's ethics, was willing to accept that pleasure is, in fact, the good. One argument he gave was that pain is clearly bad. Since pleasure is the opposite of pain, it must be good. Spusippus refuted this. He admitted that pain is bad, but that doesn't mean pleasure is good. If happiness lies in a quiet, neutral life, then it could be a golden mean between the two extremes of pain and pleasure, both of which would be bad. Plato's successors then tackled a fairly wide range of topics, carrying on the logical, metaphysical, and ethical activities of the academy. Over at the Lyceum, they were also keeping the flame alive. In this case, we have the advantage that the torch was handed to a man whose writings are partially preserved today. This was Theophrastus, whom we already met as a partner in Aristotle's biological investigations on the island of Lesbos. In fact, Theophrastus hailed from the city of Ephesus on Lesbos. Perhaps there was something of a division of labor here, because Theophrastus developed an expertise in plants to rival Aristotle's zoological prowess. His surviving writings about plants are valuable evidence of ancient ideas about botany, classifying plants into their types in true Aristotelian manner. Another work, On Stones, does a similar classificatory and descriptive job for the mineral world. Theophrastus seems to have been concerned to fill out and complete Aristotle's natural philosophy, by explaining features of the inanimate world and minor topics Aristotle had left unexplained. For instance, he wrote about the causes of dizziness and sweat. His master had not left only a body of texts, but implicitly a whole research program that could be pursued by his students. Not that those students followed Aristotle slavishly. Theophrastus is known to have raised some challenges to Aristotle's definition of place, for example. His combination of fidelity and creativity is on display in his most important surviving work, usually called the metaphysics. Here, Theophrastus creatively fuses together ideas from Aristotle's physics and his metaphysics to explain the principles of the universe, for instance, how God influences our cosmos through heavenly motion. Although he is weaving a tapestry out of Aristotelian threads, Theophrastus introduces a naughty problem here and there. He generally accepts Aristotle's teleology, the view that nature does nothing in vain, but he wonders what the purpose of some natural phenomena might be, for instance, why men have nipples or why deer lose their antlers. Aristotelianism did not die with Theophrastus. His successor, Strato, was another specialist, in this case concentrating on physical theories rather than empirical research like Theophrastus. There was also Eudemus, who may have edited Aristotle's Eudemian Ethics, hence the name, and whose area of expertise was mathematics. Aristoxenus, the fellow I mentioned who relays the story about Plato's lecture on the good, wrote about music. But all these figures died by the first half of the third century BC. We have to wait until the end of the first century, around the time of Cicero and the demise of the Roman Republic, for a resurgence of Aristotelianism. Even then, though, Aristotle's immediate successors were not forgotten. Theophrastus imitated his master by writing down a good deal of information about earlier Greek philosophical ideas. So later reports on the Presocratics frequently draw on works by Theophrastus. In fact, he may be the most important conduit for Presocratic philosophy apart from Aristotle himself. Really important was his critical discussion of pre-Eristotelian theories of sensation, which we know through a later adaptation of the Theophrastian text. Clearly, the old academy and the early Peripatetics do not represent anything like a high point of ancient thought. These were minor thinkers who carried on the work of the two greats, Plato and Aristotle. History has passed a severe judgment on them insofar as their texts are mostly lost. But what we do know suggests what might have been had ancient philosophy settled immediately into the pattern that would eventually prevail in late antiquity. A few centuries ahead, Platonism will contend with, and ultimately be reconciled with, Aristotelianism. Platonists will write commentaries on Aristotle, sometimes attacking him, but usually just expounding and explaining him. The two traditions will make common cause against shared enemies. In order for all that to happen, perhaps, the Platonists and Aristotelians needed some enemies worth uniting against. And the intervening few centuries will certainly provide that, as several new philosophical schools arise in the period we call the Hellenistic age. Some Hellenistic philosophers will endorse hedonism, while others reject pleasure as a matter of complete indifference. Some will develop new logical techniques, and set out an epistemology so ambitious it would make even Plato blush, while others find they have to reserve judgment since they are unable to believe anything at all. Next time, there will be something for everyone, as I introduce the Hellenistic schools, here on the History of Philosophy, with new intro music to go with a new period of philosophy, but without any gaps.