 Hi, I'm Peter Adamson and you're listening to the History of Philosophy podcast, brought to you with the support of the Philosophy Department at King's College London and the LMU in Munich, online at historyoffilosophy.net. Today's episode, There and Back Again, Zabarela on Scientific Method. At some point you've probably heard a young child explain the plot of a movie. Even if it's one you've seen yourself, you may find it hard to follow. If you'd asked me to explain my favorite movie to you when I was eight years old, I would have said something like, first you see a little ship and then a big ship and then and then the two funny robots are wandering around in the sand and then later they all get squeezed in a rubbish dump. And at the end the death star blows up because of the force. Of course, even adults vary in their ability to convey the plot and tone of a movie. This is why we turn for advice to professional film critics, though maybe we shouldn't given that the famous critic Pauline Kael said of Star Wars that it has no emotional grip and suffers from an absence of wonder, the greatest cinematic misjudgment since someone suggested that Buster Keaton's movies would be better if they weren't silent. It's also why Hollywood insiders pride themselves on being able to give an elevator pitch, which distills a vision for a movie down to just one or two big ideas. It's a samurai epic, but in space. Though philosophers claim to prize clarity when trying to convey their own ideas, in practice some are easier to follow than others. In the more difficult category, one thinks inevitably of Martin Heidegger. His most important work, Being and Time, is so difficult to read that Edmond Husserl, himself not the most lucid of writers, had his wife ask for a face-to-face meeting with Heidegger. She wrote that Husserl had occupied himself the whole vacation exclusively with its study and finds it necessary to let himself be instructed with you about much that does not want to become entirely clear to him. Ancient and medieval commentators would have sympathized, except that they didn't have the luxury of sitting down with their own favorite author to ask him what in the world he was talking about. That author was, of course, Aristotle. His works are sufficiently obscure that it became standard for commentators to offer excuses for their difficulty, saying for instance that this was intended to discourage non-expert readers. It may have seemed particularly galling that Aristotle did not write more clearly, given that Aristotle was renowned as a master of clear thinking. He had invented logic for goodness sake. And in the treatise that was considered the culmination of his logical works, The Posterior Analytics, he laid out a theory of demonstration that seemed intended as the ideal method for setting out scientific truths. Why then did he not use this method when he wrote about other topics? There are plenty of philosophical arguments in Aristotle's works on natural philosophy, the soul, metaphysics, and ethics, but these arguments rarely, if ever, satisfy the stringent criteria for demonstrative proof laid down in his analytics. Jacopo Zabarella, a professor at the University of Padua in the 16th century, felt about Aristotle the way I felt about Star Wars as an eight-year-old. He proclaimed to be second to no mortal in admiration of Aristotle. Of course, Aristotle was a man, not a god, and had not treated all topics and science so exhaustively as to render further efforts superfluous. Still, he had planted the seed and made the basis from which even the things he did not write about can be known. So Zabarella was at pains to show that Aristotle's works were in fact well-designed for the student who would be reading them. For a thousand years and more, it had been common for commentators to uncover the demonstrative arguments lurking hidden within the apparently non-demonstrative writings of Aristotle. Zabarella knew this strategy well, having read Averroes and the Greek commentaries that were now circulating in printed versions, but he adopted a different approach to understanding Aristotle by contrasting what he called the method of the sciences to the mere order of teaching that is to be used when writing for students. As Zabarella noted, this contrast could take inspiration from one made by Aristotle himself between that which is better known or primary relative to us and that which is primary in itself. Primary in themselves are the fundamental causes and principles in a science. In ancient physics, this would have been, among other things, the four elements, fire, air, water, and earth. In a modern context, it might be something like atomic particles and the way their number and arrangements give rise to physical properties. But such foundations are not primary relative to us. To the contrary, the atomic foundations of chemistry are so obscure to humankind that even Aristotle didn't figure them out, and they were still being uncovered when Buster Keaton made his silent movies. Now, Zabarella would say that when you are teaching, you should not start with things like this. Instead, it is good policy to begin with things that are familiar or obvious to the student. In Aristotle's terms, these would be the things that are better known to us, not the things that are primary in themselves. Thus, if explaining chemistry, you might begin by showing your students a simple chemical reaction and only then go on to say how this reaction can ultimately be explained through the interaction of atomic particles. Or, if explaining Star Wars to an American audience, you might refer not to the Japanese samurai films that helped inspire it, but other science fiction epics. It's like Star Trek, you might say, but with better jokes and more dirt. This basic contrast between a discussion that works towards principles and a discussion that begins from principles was familiar in the commentary tradition. Ivaroides in particular had mentioned it in his commentary on Aristotle's physics. He distinguished between the opening move in science where we trace a sign or effect back to its cause, and a further step where on the basis of that cause we explain the effect from which we've started. As we'll be seeing, this was a core idea of Zabarela's scientific method too. But he claimed originality for his own contrast between order and method, especially insofar as it provided a tool for analyzing much debated text from Aristotle's writings. According to Zabarela, these writings are arranged in such a way that the order of presentation mirrors the order of discovery. In other words, Aristotle teaches by taking us step by step along a path he has already traveled, explaining everything in the order he came to understand it himself. Thus, his exposition does not begin with the deepest insights and most fundamental principles, but goes gradually from the obvious to the obscure, from the posterior to the primary. Zabarela offers a few examples of this from Aristotle's texts. The most basic of the five senses is touch, and it is shared most widely by different kinds of animals. Yet in his treatment of sensation, Aristotle discusses vision first because vision is the most striking and obvious kind of sense perception. It is, in other words, primary to us, not in itself. Aristotle also discusses humans in his natural philosophy before moving on to other animals, even though humans are only one kind of animal, so that animal nature is more fundamental than human nature. Or, take a case Zabarela discusses in greater detail, Aristotle's demonstration that natural bodies are ultimately made of prime matter. Prime matter is the featureless, pure potentiality that underlies concrete materials like the four elements, wood or flesh and bone. Obviously, prime matter is not better known relative to us. To the contrary, it is basically a theoretical postulate like the subatomic particles of modern science which were initially posited without being directly observable. But according to Zabarela, Aristotle proves that it exists by pointing to cases of change that we can observe, and then observing himself that there must be something that underlies every change and survives through the change, like when one and the same human is at first uneducated, then becomes educated. Prime matter is what underlies all change, so it is the principle that explains why natural bodies are changeable. As Zabarela suggested, we can think about this discovery of principles as a discovery of causes. Usually what is obvious to us is the effect, not the cause. We feel heat every day but don't realize it is caused by the element of fire, or in modern physics the agitation of particles in a body. We observe things changing but do not realize that prime matter is an ultimate cause of change, in this case what Aristotelians would call a material cause. In his writings, Aristotle follows an order of teaching that makes it possible to learn better and more easily, as Zabarela puts it. That means laying out the process of observation or argument that led to the discovery of the cause. But this part of scientific method only establishes what the cause is. In Zabarela's Latin scholastic terminology, it provides a proof quod, or quia. Once we know what the cause is, we can use it to explain the effects from which we started. That will be a more perfect kind of proof, in fact a real demonstration, precisely because it is explanatory. Zabarela, again following earlier scholastic terminology, calls it a demonstration propter quid, meaning because of what. So, to use the same example, we feel heat all the time but have to do some investigation to figure out what exactly is causing the heat we feel when we, say, put our hand near a lightsaber. It's the agitation of the air molecules around the laser thingy. Once we've done this, we'll be in a position to give a properly scientific explanation of heat by saying that it is caused by agitated molecules. Now, there is an obvious potential problem here, one that worried Zabarela enough that he devoted a small treatise to it entitled On Regress. The problem is that the whole procedure sounds circular. We first establish the cause on the basis of the effect, then go on to explain the effect by appealing to the cause. Doesn't this involve arguing from A to B and then from B back to A? Again, Zabarela was not the first to notice this difficulty. It had been a topic of discussion at Padua as far back as Paul of Venice. But Zabarela provided the definitive solution, namely that there is no circularity involved because the two kinds of reasoning are different. Scientific method, which is demonstration in the strict sense, comes only at the end of the whole procedure, when we use the cause to explain the effect. The initial stage, where we only determine what the cause is, is not demonstrative in the strict sense, and it doesn't really have the ambition of explaining anything, because you don't explain a cause on the basis of the effect, but rather vice versa. We can call the first stage progress as we move towards the causal principles, then we regress back to the effects. This is admittedly a case of retracing our steps, but with a different kind of understanding. Now we are giving solid scientific explanations of the phenomena from which we began. Zabarela thinks that this is what Aristotle meant in a passage that compares philosophical method to a u-shaped race track, where the competitors have to reach a bend at one end of the stadium and then return to the end where they started. Zabarela makes a further point that may help us to see why the method he describes is not circular. He borrows an idea from his fellow Paduan philosopher Agostino Nifo by saying that, upon establishing what the cause is, we should pause to think about its nature. This step of examining or considering the cause, which Zabarela, following Nifo, calls a negotiation of the understanding, allows us really to understand the principles we'll be using in our scientific explanations. Again, the example of prime matter is a useful one here. It's one thing to understand that something or other underlies all change in nature, it's another to understand what that underlying thing is. Upon reflection, we may see that, if it underlies all change, it must be capable of taking on any natural property, and cannot have any properties in its own right, like by being hot or dry, as fire is. Rather, prime matter is in itself only potentially all the things into which it can change. By having a better grip on the causal principle, we'll wind up with a deeper understanding of the phenomena that are the effects of this causal principle. Thus, Zabarela says that we initially had only a vague or confused grasp of the effect, but once we have gone up to the principles and back, our grasp of that same effect becomes distinct. Another contrast that Zabarela uses to account for all this, one he takes especially from the ancient Dr. Galen, is that between resolution and composition. The idea here is that, when presented with a complex phenomenon, you can resolve it into its components or principles. We can think about this as breaking something down to its basics. When you get down to these fundamental parts, you can then explain what you started with by showing how the parts are brought together. This is the stage of composition. The most obvious illustration would be the analysis of something's physical constituents. You might be investigating an almond croissant, and realize it is sweet because it contains sugar, and fattening because it contains butter. But it should work with more abstract examples too, like how Star Wars is made by mashing together tropes borrowed from samurai epics with ideas about space exploration and bad guys based on European fascists. These examples are a little bit misleading though, and not only because neither a samurai nor fascists can make the jump to hyperspeed. Films and almond croissants are not phenomena we encounter in nature. They do not grow on trees. If they did, I'd have an almond croissant orchard. So in these cases, someone like George Lucas or a pastry chef had to start with the fundamental components and put them together to achieve the desired result. In other words, the process begins with composition, not with resolution. This is typical of the practical or productive arts and sciences, according to Zabarela. The producer has some purpose or end in mind, and thinks consciously about how to reach that end through composition. He refers here to house building, one of Aristotle's favorite examples. When someone builds a house, they begin with bricks and beams, and have to put the house together. In the study of nature, by contrast, we are presented with already complete, complex things that need to be traced back to their causal principles by resolving them into those principles. Only after doing that can we explain the natural phenomena on the basis of those causes, performing composition by seeing how the causes come together to produce the complex results we originally started from. So the there-and-back-again structure described by Zabarela is really only appropriate for non-productive or theoretical sciences, especially the branches of natural philosophy like physics and zoology. His vaunted method is not applicable to practical contexts like the technological arts or ethics in political philosophy, where one begins from the desire to pursue some end, rather than from observed phenomena that need explanation. Zabarela's focus on theoretical philosophy and his treatment of natural philosophy as the paradigmatic kind of science makes sense in biographical and institutional terms. He began in Padua as a professor of logic, and later took up the chair of natural philosophy. His theory brings together these two parts of the university curriculum. As he says himself, the sciences are nothing more than logic put to use, and his works on scientific methodology are in turn nothing more than an attempt to show how logic, especially the theory of demonstration, is used in natural philosophy. One might add that the prestige of natural philosophy at the University of Padua matches the central role natural philosophy occupies in his theory. If this is only to be expected, it is no less predictable that within the competitive atmosphere of Italian scholasticism, Zabarela's theory would be attacked by a rival. This was Alessandro Piccolomini, another philosopher at Padua who denied that the best order of teaching is the order of discovery. To the contrary, one should often begin by explaining first principles to the students. So unlike Zabarela, Piccolomini would encourage a chemistry teacher to welcome students on their first day by presenting them with the theory of the atom, since it is fundamental for everything else they will learn. Piccolomini was also much more interested in metaphysics than Zabarela was, and stressed the dependence of natural philosophy on this higher science. Against this, Zabarela contended that the study of nature is independent of metaphysical considerations which he leaves to the theologians. This is just one respect in which Zabarela and the Paduan thinkers leading up to him anticipated later ideas about science, ideas we associate more with the Enlightenment. We saw last time how Pompanazzi offered an account of soul and intellect that was deliberately independent of religious belief. He was not apologizing when he said that his account agrees with reason and experience, it maintains nothing mythical, nothing depending on faith. Likewise, Zabarela highlighted the empiricist side of Aristotle, writing that in the investigation of nature, all our knowledge takes its origin from sensation. Scholastics in this period also contrasted a priori and a posteriori knowledge, which is terminology that will become very familiar in later periods of philosophy. Whereas a posteriori knowledge is based on sensation, the kind of understanding Zabarela associates with natural philosophy, a priori knowledge is used in fields like mathematics that do not base themselves on empirical observation. Still, before leaping to the conclusion that Zabarela was a forerunner of empiricists like David Hume and John Locke, we should pause over his comments about induction. He expects only modest gains from a strictly inductive investigation. This is not on the grounds famously mentioned by Hume that induction can never rule out future counterexamples. Rather, it is because Zabarela thinks that induction is only a generalization of some obvious fact, and fails to reveal the essential natures of things. So for instance, you can use induction to notice that all humans are two-footed, something that would need only light confirmation, as he says, and this would presumably involve checking out enough humans to satisfy yourself that they are indeed two-footed by nature. Induction would not, by contrast, allow you to realize that a triangle has internal angles whose sum is 180 degrees. For that, one would need to do a proper scientific investigation. Zabarela gives that example because it is mentioned by Aristotle, not because he is particularly interested in mathematics. He is mostly happy to stay within his remit of logic and the study of nature, and the union of the two that is his treatment of scientific method. Thus, he has little to say about the a priori realm, and quite a bit about the various branches of natural philosophy. As we've seen, these are to be approached empirically, but also to be considered as theoretical sciences, which just means that they are undertaken purely for the sake of knowledge and not for pursuing some end or to make some product. For this reason, Zabarela insists that medicine does not really belong to natural philosophy. It does, after all, pursue a practical end, namely the health of the patient. So he rigorously distinguishes the explanatory accounts that undergird medical treatment, the theory of the four humours, for instance, and in general whatever belongs to physiology and zoology, from medicine as an applied art. This too can be seen as a way to pull rank within the university context. As an expert on Aristotelian natural philosophy, Zabarela was pleased to be able to tell his colleagues who taught medicine that the real science behind their activities was to be found in a work like Aristotle's Parts of Animals. But this was far from being the last word on science in the 16th century, at Padua and elsewhere. In coming episodes, we'll be exploring both of the disciplines just mentioned, mathematics and medicine, and seeing that many scholars were, unlike Zabarela, more than happy to step outside the confines of Aristotelian science. But before we turn to these topics, I want to wrap up our look at Paduan Aristotelianism and Averroism by looking more deeply at the impact of the commentaries of Averroes and other sources from the Islamic world. In a return no less welcome than that of the Jedi, Dag Nicholas Hase will be coming back to the podcast to tell us all about the reception of Arabic philosophy in Renaissance Italy. I'm not forcing you to listen to it, but if you do miss it all I can say is, I'll find your lack of faith disturbing. That's next time here on The History of Philosophy, without any gaps.