 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 www.historyoffilosophy.net. Today's episode, Origin of Species – Roger Bacon Around the turn of the 13th century, a young man from the town of Assisi, in the center of modern-day Italy, informed his father that he wouldn't be going into the family business. In fact, he wouldn't be going into any business at all, unless you count caring for lepers and preaching to birds as a business. The young man's name was, of course, Francis. By the time of his death in 1226, he had started a movement that would transform Christianity across Europe. The followers of Francis of Assisi were the Franciscans, just one of several mendicant orders who emerged in the 13th century. The term mendicant refers to the fact that they were sworn to poverty and survived on charitable donations alone. The members of mendicant orders, sometimes called friars, posed a challenge to the established church. Their devotion to a life of humility and poverty served as an unspoken, and sometimes spoken, rebuke to the wealth of bishops and the worldly entanglements of popes. A clash was inevitable. As we'll see in a few episodes, it came in the form of agonized debate over the mendicant ideal of absolute poverty. More surprising was the role that the Franciscans came to play in the medieval universities, and thus in the history of philosophy. Francis of Assisi himself was no scholar. He led a life of simplicity, without the adornment of book learning, which could so easily lead to pridefulness. But already in Francis's lifetime, the friars of his order began to take instruction in church doctrine and theology from lecturers. Robert Grozetest, subject of last week's episode, was not himself a member of the order, but did serve as the first lecturer to the Franciscan friars in Oxford. There he may have met, if not actually taught, Roger Bacon. Along with Bonaventure and Peter Olivey, Bacon is the first of three outstanding Franciscan thinkers who are going to be occupying our attention in the next several episodes. Later on, after considering figures from another mendicant order, the Dominicans, we'll be meeting two other great Franciscan philosophers, Duns Scotus and William of Ockham. But I'm going to follow the lead of Walter White celebrating his birthday on Breaking Bad and start things off with Bacon. This is not for reasons of chronology. Roger Bacon actually outlived Bonaventure by some 20 years, dying in the early 1290s, whereas Bonaventure died in 1274. Rather, it's because he takes our story on directly from Robert Grozetest. Bacon carried on Grozetest's intellectual project, by adopting and expanding on his idea of a science founded in experience, and by exploring the problems of light and vision that drove Grozetest's innovations in physics. He also admired Grozetest's activity as a translator, valuing his productions far higher than those of more famous contributors to the translation movement such as William of Moerbeke. Grozetest was one of the few contemporaries who managed to earn Bacon's respect. Another was Adam Marsh, a student of Grozetest whose lectures Bacon was able to attend in Oxford. Bacon was also a student and master at the University of Paris, where he encountered such heavyweights as Alexandre of Hales and William of Auvergne. Because he went back and forth several times between Paris and Oxford, Bacon had a deep familiarity with the scholastic culture on both sides of the channel. He was not particularly impressed. Alexandre of Hales, he noted, represented an older generation which still lacked access to the full range of works in natural science and metaphysics because translations were not yet available or because their study was banned in Paris. Earlier still, luminaries like Gratian, Peter Lombard, and the Victorines had been unaware of the philosophical riches that would be unearthed in the translation movement. They might thus be forgiven for their slighting references to the sciences, but there was no excuse for Bacon's own contemporaries, who were failing to engage with the Aristotelian tradition as Bacon himself set out to do. Because he was so disappointed by most of the Latin translations he could consult, and because he was doubtful that any translation can capture the full meaning of an original text, Bacon devoted himself to the study of languages. He mastered Greek and Hebrew, and encouraged others to do the same. Above all, he implored the church authorities to make sciencia experimentales, or science based on experience, fundamental to the university curriculum. He made his pitch in a series of works addressed to Pope Clement IV in the 1260s. These were written at the explicit invitation of the Pope, which gave Bacon an exemption from his order's rule against publishing works for wider circulation. The result was a frenzy of scholarly activity, intended to demonstrate the utility and acceptability of the sciencia experimentales. Discoveries made in natural philosophy could not just put theology on a sound foundation, they could help in just about every area of human endeavor, from statecraft to warfare. In one astonishing passage, Bacon proposes the possibility of building chariots that can power themselves, a flying machine like a bird but with artificial wings, and instruments for diving to the bottom of rivers or the sea. To persuade us of the viability of the last scheme, he mentions how Alexander the Great had himself lowered in such a device to do some deep-sea exploring, a legend also recounted by the Muslim historian Ibn Khaldun, who found it much harder to swallow. Though he was an imaginative enough man to look forward to the invention of the car, plane, and submarine, Bacon spent most of his time looking to the past. He was convinced that the ancients were more advanced in the sciences than the men of his own age. Not so much the ancients in general, but Aristotle in particular. For Bacon, Aristotle was one of the few who have achieved a complete, or nearly complete, understanding of philosophy. No one has matched the insight achieved by the earliest Biblical figures such as Adam and Noah, and by Solomon, who was the first to revive science after a period of oblivion. Later, there was another revival thanks to the Greeks and especially Aristotle, and here Bacon hastens, like many an ancient Christian, to say that Hellenic science was all borrowed from the Hebrew tradition. Since Aristotle, Bacon believes that only Muslim thinkers have come close to the same level of understanding, and especially Avicenna. In his quest to take a place of his own in this pantheon of greats, Bacon emphasizes again and again the indispensable role of sense experience. He admits that human souls may have some sort of innate knowledge within them, but we cannot access this knowledge because of our fallen and bodily state. So we are effectively born as blank slates, and unless we are fortunate enough to enjoy a direct illumination from an angel or god, we are on our own. We must learn through close observation of nature and other personal experiences. As Bacon says, knowledge achieved in this way is better than knowledge achieved through abstract proof. He applies this even to mathematics. It is one thing to follow the logic of a proof for the first proposition of Euclid's elements, another to have the intuitive insight provided by a visible diagram that accompanies the proof. Bacon is above all renowned for his application of mathematics to natural philosophy, and I'll get to that shortly, but he was a multifaceted thinker who made innovations in a whole range of fields. We can see this for instance from his work in The Philosophy of Language. Given Bacon's philological activities and his extensive training in the logical arts, it was natural for this to become one of his abiding interests. And given his irreverent and creative mind, it's natural that he would take an unusual approach. He pays particular attention to what we might nowadays call semiotics, that is the study of signs. Usually he has in mind significant language, but street signs and even the noises made by animals would count as signs as well. Here, Bacon is taking up a theme explored in the works of Augustine, but unlike fellow Franciscans such as Bonaventure, Bacon did not really see himself as an Augustinian. He tries to persuade us that he developed his own ideas about signs without even consulting Augustine's works. Bacon holds that significant language is conventional in nature. The meaning of our words is entirely artificial in contrast to natural signs like the barking of a dog. Language is thus a tool that we fashion for ourselves. Indeed, words can only have meaning when they are used by someone who has the intention to signify. In the first instance, this will be the person who first used a word to signify some existing thing. The meaning of the word is set by the intention of this original name-giver. Whoever first applied the word bacon to cured pork determined that cured pork is what the word bacon would signify. But since language is entirely conventional, others are free to take the same word and use it differently. This gives rise to the possibility of equivocation. If I use the word bacon to refer to cured meat, but you use it for a 13th century philosopher and scientist, we are using the word with two entirely different meanings, or equivocally. Bacon, the philosopher, not the cured meat, thinks that equivocation is a complex phenomenon which none of his predecessors managed to explore fully. It comes in different types, which may be closer to or further away from the unifical use of a word. Using a word unifically means using it in exactly the same way on two occasions, as when I offer you bacon for breakfast and then later ask if you'd like bacon for lunch too. Furthest from this unifical use is applying the same word to something that exists and then something that doesn't exist. This is because the existent and the non-existent can share nothing in common at all. As Bacon puts it, the distance between them is infinite. His position here is a bit puzzling. You'd think that the name Roger Bacon, which was used during his life to refer to him, can still be used now that he is dead in exactly the same way, without any equivocation at all. But Bacon's remarks on the non-existent fit with his idea that the original name-giver always seeks to signify some existing thing. Once the thing no longer exists, the act of signifying cannot possibly be the same. From here, Bacon goes on to provide a list of types of equivocation, from most to least equivocal. There's the use of words to signify two things that have a relation. The classic example here is healthy, which can be applied to a person or to the sort of food that helps a person to be healthy. A diametrically opposed example might be bacon bits, a rather alarming and certainly unhealthy offering found in many American salad bars. Bacon bits stand in some kind of relation to real bacon, though perhaps only the manufacturers know exactly what that relation is. Another form of equivocation is when the same word is used to refer to both a genus and a species. I might talk of Bacon generally at one time, and Canadian Bacon at another. Finally, the slightest form of equivocation is when a word is used with the same meaning but different grammatical form. I'm not able to illustrate this with Bacon, but Roger Bacon himself points out that it works with eggs. In Latin, the word ovum means egg in both the nominative and accusative case. Given that he is analyzing language and not doing theology, Bacon only occasionally touches on the implications of all this for talking about God. Unlike many medieval thinkers, he's confident that humans can use language to refer to God. He suggests that this may be achieved through a relation or analogy between God and the things he creates. This is a proposal we'll be seeing again when we get to Thomas Aquinas. And speaking of seeing, let's now turn to a more famous aspect of Roger Bacon's thought, his theory of light and vision. I've said already that here, he continues the efforts begun by Robert Grossetest. But whereas Grossetest's natural philosophy traced all things back to the propagation and multiplication of light, Bacon is going to go the other way, explaining the propagation of light in terms of a more basic set of physical principles. The word at the heart of his physics is species. This is potentially confusing because we've so often seen this word in the context of logic, as when species is contrasted to genus. Originally, the Latin word speciase means the outward appearance of something, and that's somewhat closer to the way Bacon is using it. A good English rendering might be likeness. Bacon's idea is, then, that natural things influence the world around them by imposing their species, or likeness, on other things. Hence, Bacon's official definition of species as, the first effect of any natural agent. A basic example might be fire, which affects nearby bodies by giving them the species of heat. Bacon sees this as the mechanism that underlies all physical interaction. Sound, for instance, is a species produced by vibration, so that the excitement of particles involved in frying Bacon causes a sizzling noise that is impressed on the air and then your ear. When you taste the Bacon, the species is the taste that is communicated to your tongue and thus to your sense faculty. And illumination, of course, is the propagation of a species from a light source. Though species like these, which are available to our outer senses, are the most obvious examples, Bacon's theory can be applied more widely. He alludes to Avicenna's case of the sheep that perceives hostility in the wolf and agrees with him that a faculty called estimation in the sheep receives the species of the wolf's hostility. Bacon denies that in producing a species, things are somehow sending out parts of themselves, which would be lost, like the sheets of atoms that are thrown off of things in the visual theory of ancient atomism. Strictly speaking, species are not emitted at all. Instead, the influence of the natural agent causes a potentiality to be realized in the thing it affects. This can occur only through direct contact. So if a light source is to illuminate a visible object, it needs first to actualize the potential illumination of the air that is immediately surrounding it. This illuminated air then affects the air next to it, and so on, until the species of illumination is realized in the visible object. The same is true for the propagation, or as Bacon calls it following Grossetest, the multiplication, of any species. For this reason, Bacon thinks that all natural action requires a medium. It would be impossible in a void. Thus in vision, there needs to be air, or some other transparent medium, between the light source and the lit-up visible object, and between the object and the viewer. Even though the medium is absolutely required for the multiplication of species, it also inhibits the transmission of the natural effect by offering resistance. This is one reason why the influence becomes less pronounced as one gets further away from the original source. You feel less heat from a frying pan if you stand on the far side of the kitchen. On the other hand, Bacon thinks that the mere process of being successively multiplied also causes a gradual weakening of influence. This may remind us of the ideas put forward by earlier 13th century physicists like Richard Rufus. They propose that a force impressed on a moved body will wear out by itself in addition to being impeded by the air or other medium through which the projectile moves. Obviously Bacon's theory is especially well-suited to explaining the propagation of light, and he does apply it especially in that context. He confronts the age-old question of whether we see by sending something out from our eyes like visual rays, or by receiving some influence that comes to the eyes from the visible object. His answer? Both, of course, because all natural things influence their surroundings. By this rule, the sense organ too must cause a multiplication of species, even if it also receives the species of what it sees. It may seem superfluous that the eye should actively do something to its environment as well as being affected by a species coming from the object. But Bacon thinks there is empirical evidence to support his two-way theory. The fact that cats' eyes gleam in the dark shows that they are sending out visual rays, while the after-images of bright lights that we see after we turn away from those lights shows that our eyes have been affected. With all of this, Bacon is drawing on the visual theories of the Muslim scientist Ibn al-Haytham, whose works he studied with great care. He played a major role in the transmission of Ibn al-Haytham's theories in Latin Christendom to the point that Bacon's version of those theories will remain the standard account of eyesight until Kepler in the 17th century. But his ambition to situate optics within a more general physics shows the influence of another source from the Islamic world, a text called On Rays, which is ascribed to the earlier Muslim thinker Akindi. This treatise invokes the mechanism of rays to explain not just light and vision, but other natural influences like sound, as well as the more occult powers involved in astrology and magic. Bacon's multiplication of species is an updated version of the same theory, and Bacon tends to agree with Akindi that the natural philosopher should take an interest in astrological and magical influence. He is also an enthusiastic believer in the science of alchemy. We need to be cautious approaching this aspect of Bacon's thought, where he explores what we would nowadays call pseudoscience. When he uses the word magic, it is always because he wants to draw a distinction between the fraudulent claims of magicians and his own science of experience. Experience demonstrates that stars do exert an astrological influence, but we should not follow Akindi and others who went so far as to say that the stars actually determine all future events. Rather, astrology can provide only probable conjectures, and is at its most reliable when predicting general phenomena, like weather patterns. Similarly, when it comes to alchemy, we need to base our practice in experience. For Bacon, this means understanding that bodies are composed from four fundamental ingredients, the so-called humours. Alchemy is the art that studies and learns to manipulate these ingredients and their effects. It was of course standard medical theory that human and other organic bodies are made up of the four humours, but he is unusual in applying this scheme to non-organic things, like minerals and metals. Bacon has an almost obsessive interest in the possible applications of this theory, and especially in the use of alchemy and medicine to prolong the span of one's life. In a passage that brings together many of his scientific interests, Bacon explains how to produce an elixir of longevity. First, get an alchemist to make you a mixture which is perfectly balanced in its humoral properties. Next, have an astronomer tell you the propitious moment in terms of astral influence. Finally, ask a specialist in geometrical optics to set up mirrors so that they will focus the astral rays on the mixture, transmitting the celestial virtue into it. Of course, if you are lucky enough to find yourself in Paris or Oxford in the 13th century, you'll only need to find one specialist to carry out all these tasks, Roger Bacon himself. But something must have gone wrong, because Bacon did not live an extraordinarily long life, but then we all know that Bacon is unhealthy. Nor did his astrological investigations help him to avoid misfortune in his later years. In the late 1270s, he was caught up in a church crackdown on deviant philosophical teachings, which included, among other things, condemnation of belief in magic. Bacon's frequent diatribes against magic were probably intended not only to mark the boundaries of proper science, but also to shield him against precisely such condemnations. If so, they didn't work any better than his experiments with longevity, and he found himself imprisoned briefly for his unorthodox teachings. Nowadays he gets a warmer reception. Despite his flirtations with the occult, he has, like Robert Grossetest but with considerably more plausibility, been held as a pioneer in experimental science, a worthy forerunner to a man who shared not just his name, but his scientific attitude, the Renaissance thinker Francis Bacon. But in our zeal to detect the early stirrings of modern science in the medieval age, we shouldn't overlook the historical and philosophical importance of the arts of magic and astrology. Indeed, I feel that with regard to this topic, we're like the bacon at a British sandwich shop on a roll. So join me next time for an episode that I'm sure will leave you spellbound as I discuss medieval magic with the world's leading expert on the topic, Charles Burnett, here on The History of Philosophy Without Any Gaps.