By the beginning of the thirteenth century European science was on the rise, stimulated by the enormous influx of Greco-Arabic works translated into Latin and used at the new universities that sprang up all over Europe, supplanting the cathedral schools of the earlier medieval era.
The earliest of these institutions of higher learning was the university of Bologna, founded in 1088, followed in turn by those of Paris (ca. 1150), Oxford (1167), Salerno (1173, a refounding of the medical school), Palen-zia (ca. 1178), Reggio (1188), Vicenza (1204), Cambridge (1209), Salamanca (1218), and Padua (1222), to name only the first ten, with another ten founded in the remaining years of the thirteenth century. Twenty-five more were founded in the fourteenth century, and another thirty-five in the fifteenth, so that by 1500 there were eighty universities in Europe, evidence of the tremendous intellectual revival that had taken place in the West, beginning with the initial acquisition of Greco-Arabic learning in the twelfth century.
Bologna became the archetype for later universities in southern Europe, Paris and Oxford for those in the northern part of the continent. Bologna was renowned for the study of law and medicine, Paris for logic and theology, and Oxford for philosophy and natural science. Training in medicine was based primarily on the teachings of Hippocrates and Galen, while studies in logic, philosophy, and science were based on the works of Aristotle and commentaries upon them, at first translated from Arabic and then later from Greek.
Although Aristotle's works formed the basis for most nonmedical studies at the new universities, some of his ideas in natural philosophy, particularly as interpreted in commentaries by Averroës (Ibn Rushd), were strongly opposed by Catholic theologians. One point of objection to Aristotle was his notion that the universe was eternal, which denied the act of God's creation; another was the determinism of his doctrine of cause and effect, which left no room for divine intervention or other miracles. Still another objection was that Aristotle's natural philosophy was pantheistic, identifying God with nature, which derived from the Neoplatonic interpretation of Aristotelianism by Avicenna (Ibn Sina).
This led to a decree, issued by a council of bishops in Paris in 1210, forbidding the teaching of Aristotle's natural philosophy in the university's faculty of arts. The ban was renewed in 1231 by Pope Gregory IX, who issued a bull declaring that Aristotle's works on natural philosophy were not to be read at the University of Paris “until they shall have been examined and purged from all heresy.” The ban seems to have remained in effect for less than a quarter century, for a list of texts used at the University of Paris in 1255 includes all of Aristotle's available works.
The controversy was renewed in 1270 when the Bishop of Paris, Eti-enne Tempier, condemned thirteen propositions derived from the philosophy of Aristotle or from Aristotelian commentaries by Averroës. This gave rise to the doctrine of “double-truth,” in which an idea might be declared true if demonstrated by reason in physics and metaphysics, while a contradictory concept could be independently considered true in theology and the realm of faith. Pope John XXI, after seeking the advice of theologians, issued a bull in 1277 in which he condemned 219 propositions, including the original thirteen listed by Tempier, threatening excommunication of anyone who held even a single erroneous doctrine. That same year a similar condemnation was issued by Tempier as well as by the archbishop of Canterbury, Robert Kilwardby whose edict was renewed in 1284 by his successor, John Pecham. A number of the propositions were declared to be erroneous because their determinism placed limits on the power of God.
Meanwhile European scholars were absorbing the Greco-Arabic learning that they had acquired and used to develop a new philosophy of nature, which although primarily based upon Aristotelianism differed from some of Aristotle's doctrines right from the beginning.
The leading figure in the rise of the new European philosophy of nature was Robert Grosseteste (ca. 1168-1253). Born of humble parentage in Suffolk, England, he was educated at the cathedral school at Lincoln and then at the University of Oxford. He taught at Oxford and went on to take a master's degree in theology, probably at the University of Paris. He was then appointed chancellor of the University of Oxford, where he probably also lectured on theology, while beginning his own study of Greek. When the first Franciscan monks came to Oxford in 1224 Grosseteste was appointed as their reader. He finally left the university in 1235 when he was appointed bishop of Lincoln, his jurisdiction including Oxford and its schools.
Grosseteste's works are divided into two periods, the first when he was chancellor of Oxford and the second when he was bishop of Lincoln. His writings in the first period include his commentaries on Aristotle and the Bible and most of his independent treatises, while those in the second period are principally his translations from the Greek: Aristotle's Nichomachean Ethics and On the Heavens, the latter along with his version of the commentary by Simplicius, as well as several theological works.
Grosseteste's commentaries on Aristotle's Posterior Analytics and Physics were among the first and most influential interpretations of those works. These two commentaries also presented his theory of science, which he put into practice in his own writings, including six works on astronomy and one on calendar reform, as well as treatises entitled The Generation of the Stars, Sound, The Impressions of the Elements, Comets, The Heat of the Sun, Color, The Rainbow, and The Tides, in which he attributed tidal action to the moon.
Grosseteste was the first medieval scholar to deal with the methodology of science, which for him involved two distinct steps. The first of these was a combination of deduction and induction, which he termed “composition” and “resolution,” a method for arriving at definitions. As Grosseseste put it: “This method involves two procedures, one being by composition and the other by resolution. Aristotle teaches first the method of arriving at the definition by composition, because this method is like a progression from the more universal and simple to the more composite. The method of resolution is the opposite of that.”
The second step was what Grosseteste called verification and falsification, a process necessary to distinguish the true cause from other possible causes. He based his use of verification and falsification on two assumptions about the nature of physical reality. The first of these was the principle of the uniformity of nature, in support of which he quoted Aristotle's statement that “the same cause, provided that it remains in the same condition, cannot produce anything but the same effect.” The second was the principle of economy, which holds that the best explanation is the simplest, that is, the one with the fewest assumptions, other circumstances being equal. Here again he quoted Aristotle, who said that power from natural agents proceeds in a straight line “because nature operates in the shortest way possible.” Beginning with these assumptions, Grosseteste's method was to distinguish between possible causes “by experience and reason,” rejecting theories that contradicted either factual evidence or an established theory verified by experience.
Grosseteste believed that it was impossible to understand the physical world without mathematics. He noted that “the science that is concerned with the study of radiant lines and figures [i.e., optics] falls under geometry…; the science of constructing machines, as under architecture and other mechanical arts, falls under the science of the figures of bodies; the science of harmonies falls under arithmetic; and the science which sailors use to direct the course of ships by the appearance of the stars is subordinate to geometry.”
The use of mathematics made it essential to perform measurements that resulted in a number, though in doing so there was an inescapable inaccuracy, which made all human measurements conventional, as opposed to the certitude of geometry. But although geometry, for example, could give the “reason for the fact,” in the sense of describing a phenomenon in optics such as reflection of light, it could not provide the physical causes involved. Thus a complete explanation of optical phenomena requires not only geometry, but a knowledge of the physical nature of light that causes it to move as it does in being reflected by a mirror, in which the angle of incidence equals the angle of reflection.
Grosseteste believed that the study of optics was the key to an understanding of the physical world, and this gave rise to his Neoplatonic “Metaphysics of Light.” He believed that light is the fundamental corporeal substance of material things and produces their spatial dimensions, as well as being the first principle of motion and efficient causation. According to his optical theory, light travels in a straight line through the propagation of a series of waves or pulses, and because of its rectilinear motion it can be described geometrically. This was similar to the acoustical theory he presented in his commentary on Aristotle's Posterior Analytics, where he writes that “when the sounding body is struck and vibrating, a similar vibration and similar motion must take place in the surrounding contiguous air, and this generation progresses in every direction in straight lines.”
Grosseteste thought that the same theory, which he called the “multiplication of species,” could be used to explain the propagation of any disturbance, be it light, sound, heat, mechanical action, or even astrological influence. Thus the study of light was of crucial importance for an understanding of nature. He also believed that light, by which he meant not only visible radiation but the divine emanation as well, was the means by which God created the universe, and that through it soul and body interacted in man.
The study of optics was divided by Grosseteste into three parts: phenomena involving vision, mirrors (catoptrics, or reflection), and lenses (dioptrics, or refraction). He discussed the third part more fully than the other two, noting that it had been “untouched and unknown among us until the present time,” and suggested applications of refraction that in the seventeenth century would be realized through the invention of the telescope and the microscope. “This part of optics,” he wrote, “when well understood, shows us how we may make things a very long distance off appear as if placed very close… and how we may make small things placed at a distance appear any size we want, so that it may be possible for us to read the smallest letters at incredible distances, or to count sand, or grains, or seeds, or any sort of minute objects.”
Grosseteste developed a theory of refraction in an attempt to explain the focusing of light by a “burning-glass,” or spherical lens. An experiment would have shown him that his law of refraction was incorrect, but apparently he never put his law to the test, although it was one of the basic tenets of his scientific method that if a theory was contradicted by observation it must be abandoned.
Grosseteste's application of his scientific method is evident in his treatise The Rainbow, in which he broke with Aristotelian theory by holding that the phenomenon was due to refracted rather than reflected light. Although his theory was incorrect, he posed the problem in such a way that investigations by those who followed after him approached closer to the true solution through criticizing his efforts. His work on the rainbow inspired some verses written about 1270 by the French poet Jean de Meun in his continuation of Guillaume de Lorris's Romance of the Rose These are in chapter 83, where “Nature explains the influence of the heavens,” telling of how the clouds, “to give solace to the earth”
Are wont to bear, ready at hand, a bow
Or two or even three if they prefer,
The which celestial arcs are rainbows called,
Regarding which nobody can explain,
Unless he teaches optics in some school,
How they are varicolored by the sun,
How many and what sorts of hues they show,
Wherefore so many and such different kinds,
Or why they are displayed in such a form.
There is little in Grosseteste's writing to indicate that he was a Christian bishop, but in his treatise On the Fixity of Motion and Time he differed from the Aristotelian doctrine that says the universe is eternal, for that contradicted his belief in God's creation. His Christian beliefs are also evident in another treatise, On the Order of the Emanation of Things Caused from God, in which he said that he wished men would cease questioning the biblical account of the Creation.
Grosseteste also wrote a number of treatises on astronomy. The most important of these was De Sphaera, in which he discussed elements of both Aristotelian and Ptolemaic theoretical astronomy. He also wrote of Aristotelian and Ptolemaic astronomy in his treatise on calendar reform, Compotus correctorius, where he used Ptolemy's system of eccentrics and epicycles to compute the paths of the planets, though he noted, “These modes of celestial motion are possible, according to Aristotle, only in the imagination, and are impossible in nature, because according to him all nine spheres are concentric.” Grosseteste also wrote of astrological influences in his treatise On Prognostication, but he later condemned astrology, calling it a fraud and a delusion of Satan's.
Grosseteste's De Sphaera was written at about the same time as a treatise of the same name by his contemporary John of Holywood, better known by his Latin name, Johannes de Sacrobosco. Little is known of his life other than the facts that he became a monk at the Augustine monastery of Holywood, and that after studying at Oxford he was admitted in 1221 to the University of Paris, where he was elected professor of mathematics.
Sacrobosco's principal extant works are three elementary textbooks on mathematics and astronomy: De Sphaera, De Computo Eccliastico, and De Algorismo, all of which are frequently bound together in the same manuscript. Sacrobosco's fame is principally due to his De Sphaera, an astronomy text based on Ptolemy and his Arabic commentators, most notably al-Farghani. The text was first used at the University of Paris and then at all schools throughout Europe, and it continued in use until the late seventeenth century. His De Computo Eccliastico points out the errors in the Julian calendar, proposing a solution very similar to the reform adopted by Pope Gregory XIII three and a half centuries later. His De Algorismo, which taught the techniques of calculating with positive integers, was the most widely used manual of arithmetic in the medieval era, continuing in use until the sixteenth century.
Grosseteste's efforts in framing a new philosophy of nature were continued by Albertus Magnus (ca. 1200-1280). Born to a family of the military nobility in Bavaria, he studied liberal arts at the University of Padua, where he was recruited into the Dominican order by its master general, Jordanus of Saxony. Albertus then studied theology and taught in Germany before enrolling in the University of Paris circa 1241, where he lectured on theology for seven years before he was sent to open a school in Cologne. His students included Thomas Aquinas, who came from Italy to study with him, either in Paris or Cologne. Albertus was appointed provincial of the German Dominicans in 1253, and in 1260 he became bishop of Regensburg, a post that he resigned two years later, after which he spent the rest of his life preaching and teaching.
Albertus played a crucial role in rediscovering Aristotle and making his philosophy of nature acceptable to the Christian West. The main problem involved in the Christian acceptance of Aristotle was the conflict between faith and reason, particularly in the Averroist interpretation of Aristotelian thinking, with its determinism and its view of the eternity of the cosmos. Albertus sought to resolve this conflict by regarding Aristotle as a guide to reason rather than an absolute authority and declaring that where his ideas conflicted with either revealed religion or observation, he must be wrong. Albertus held that natural philosophy and theology often spoke of the same thing in different ways, and so he assigned to each of them its own realm and methodology, assured that there could be no contradiction between reason and revelation.
Albertus undertook the task of interpreting Aristotle at the request of his Dominican brethren, who wished to understand the Aristotelian worldview; he explains this in the prologue to his commentary on Aristotle's Physics, where he says that his purpose is “to make all parts of philosophy intelligent to the Latins.”
The most original contributions made by Albertus were in botany and the life sciences, where his work was distinguished by his acute observations and skill in classification. His attitude toward scientific method is evident in his commentary on the pseudo-Aristotelian De Plantis, the principal source of botanical knowledge until the sixteenth century, where in discussing the native plants known to him he writes, “In this sixth book we will satisfy the curiosity of the students rather than philosophy…. Syllogisms cannot be made about particular natures, of which experience (experimentum) alone gives certainty.”
Although Albertus was very modern in his scientific thinking, he was still medieval in his views on such matters as magic, divination, and astrology. He writes in his Summa Theologica of his belief that magic is due to demons: “For the saints expressly say so, and it is the common opinion of all persons, and it is taught in that part of necromancy which deals with images and rings and mirrors of Venus and seals of demons.” Albertus writes of astrology in almost all of his scientific treatises, describing the effects produced by such celestial phenomena as conjunctions of the planets, to which he attributes “great accidents and great prodigies and a general change of the state of the elements and of the world.”
Ulrich Engelbert of Strasburg, a pupil of Albertus's, describes him as “a man in every science so divine that he may well be called the wonder and miracle of our time.” Thomas Aquinas writes of him with equal admiration, saying, “What wonder that a man of such whole-hearted devotion and piety should show superhuman attainments in science.” Albertus was canonized by Pope Pius XI on 16 December 1931, and ten years later Pope Pius XII declared him the patron saint of all those who cultivate the natural sciences.
Thomas Aquinas (ca. 1225-1274) was born near Monte Cassino in southern Italy where his father served the emperor Frederick II in his war against the papacy. He began his education at the Benedictine abbey of Monte Cassino, after which he went to the newly founded University of Naples, where he was introduced to the works of Aristotle. After joining the Dominicans, he was sent for further studies to Cologne and then Paris, where his teachers included Albertus Magnus.
Aquinas spent two periods as professor at the University of Paris, 1256-59 and 1269-72, and in the interim he was associated in turn with the papal courts of Alexander IV, Urban IV, and Clement IV After his second professorship at Paris he returned to Naples to start a Dominican school, which he directed until a few months before his death in 1274. He was canonized by Pope John XXII on 18 July 1323, and subsequently he was presented by the Roman Catholic Church as the most representative teacher of its doctrines. His writings are still taught at Catholic universities.
Aquinas, like Albertus Magnus, tried to resolve the conflict between theology and natural science and show that there could be no real contradiction between revelation and reason. Arguing against those who said that natural philosophy was contrary to the Christian faith, he writes in his treatise Faith, Reason and Theology that “even though the natural light of the human mind is inadequate to make known what is revealed by faith, nevertheless what is divinely taught to us by faith cannot be contrary to what we are endowed with by nature. One or the other would have to be false, and since we have both of them from God, he would be the cause of our error, which is impossible.”
This involved him in disputes at the University of Paris in 1268-70 over the Aristotelian philosophy that he and Albertus had introduced. The condemnation of Averroist doctrines by the bishop of Paris in 1270 may have been directed against some of the teachings of Aquinas, one being that the creation of the world cannot be demonstrated by reason alone. This and other interpretations by Aquinas were his solution to the problem of adapting Aristotelianism to Christian theology, creating the philosophical system that came to be called Thomism.
The lengths to which Aquinas went can be seen in his attempt to fit the biblical account of the Ascension into the Aristotelian cosmos. According to Ephesians 4:10, Christ “ascended up far beyond all heavens, that he might fill all things,” which presented problems for Aquinas as he tried to square this with Aristotle's philosophy and his model of the homocentric crystalline spheres.
Meanwhile, in the thirteenth century, translations were still being made from Arabic into Latin. Some of these were done under the patronage of King Alfonso X (1221-84) of Castile and León, known in Spanish as el Sabio, or the Wise. Alfonso's active interest in science led him to sponsor translations of Arabic works in astronomy and astrology, including a new edition of the Toledan Tables of the eleventh-century Cordoban astronomer al-Zarqali. This edition, known as the Alfonsine Tables, included some new observations but retained the Ptolemaic system of eccentrics and epicycles.
Grosseteste's most renowned disciple was Roger Bacon (ca. 1219-92), who acquired his interest in natural philosophy and mathematics while studying at Oxford. He received an MA. either at Oxford or Paris, in around 1240, after which he lectured at the University of Paris on various works of Aristotle's. He returned to Oxford circa 1247, when he met Grosseteste and became a member of his circle.
Bacon became a Franciscan monk in about 1257, and soon afterward he experienced difficulties, probably because of a decree restricting the publication of works outside the order without prior approval. In any event, Pope Clement IV issued a papal mandate on 22 June 1266 asking Bacon for a copy of his philosophical writings. The mandate ordered Bacon not only to send his book but to state “what remedies you think should be applied in these matters which you recently intimated were of such great importance,” and “to do this without delay as secretly as you can.”
Bacon eventually replied with three works—Opus Maius, Opus Minus, and Opus Tertium—along with a letter proposing a reform of learning in the Catholic Church. He maintained that there were two types of experience, one obtained through mystical inspiration and the other through the senses, assisted by instruments and quantified in mathematics. The program of study he recommended included languages, mathematics, optics, experimental science, and alchemy, followed by metaphysics and moral philosophy, which, under the guidance of theology, would lead to an understanding of nature and through that to knowledge of the Creator.
Within the next few years Bacon wrote three more works, the Com-munia Naturalium, Communia Mathematica, and Compendium Studii Phibso-phie, the last of which castigated the Franciscan and Dominican orders for their educational practices. Sometime between 1277 and 1279 he was condemned and imprisoned in Paris by the Franciscans, possibly because of their censure of heretical Averroist ideas. Nothing further is known of his life until 1292, when he wrote his last work, the Compendium Studii Theobgii
Bacon appropriated much of Grosseteste's concept of the “Metaphysics of Light” with its “multiplication of species,” as well as his mentor's emphasis on mathematics, particularly geometry. In his Opus Maius Bacon states that “in the things of the world, as regards their efficient and generating causes, nothing can be known without the power of geometry;” he also says, “Every multiplication is either according to lines, or angles or figures.” His ideas on optics also repeat those of Grosseteste. But he does go beyond Grosseteste in his commentary on Alhazen (Ibn al-Haytham), particularly his theory of the eye as a spherical lens, basing his own anatomical descriptions on those of Hunayn ibn Ishaq and Avicenna (Ibn Sina).
Bacon clearly states his scientific method in Part VI of the Opus Maius, “De Scientia Experimentali,” which also derives from Grosseteste. There he writes of the “three great prerogatives” of experimental science, the first being “that it investigates by experiment the noble conclusions of all the sciences.” The second prerogative, according to Bacon, is that experiment adds new knowledge to existing sciences, and the third is that it creates entirely new areas of science. He also emphasizes the vital importance of mathematics in science, writing that “no science can be known without mathematics.”
Bacon used his scientific method to study the rainbow, where he improved on Grosseteste's theory in his understanding that the phenomenon was due to the action of individual raindrops, though he erred in rejecting refraction as part of the process.
Other works by Bacon include the Epístola de Secretis Operibus Artis et Naturae et de Nullitate Magiae, which describes wonderful machines such as self-powered ships, automobiles, airplanes, and submarines.
Machines for navigation can be made without rowers so that the largest ships on rivers or seas will be moved by a single man in charge with greater velocity than if they were full of men. Also cars can be made so that without animals they will move with unbelievable rapidity…. Also flying machines can be constructed so that a man sits in the midst of the machine revolving some engine by which artificial wings are made to flap like a flying bird…. Also a machine can easily be made for walking in the sea and rivers, even to the bottom without danger.
On another topic, Bacon writes that “it has been proved by certain experiments” that life can be greatly extended by “secret experiences.” One of his recommendations for achieving an exceptionally long life involves eating the specially prepared flesh of flying dragons, which he says also “inspires the intellect,” or so he was told “without deceit or doubt from men of proved trustworthiness.”
Writings such as this gave Bacon the posthumous reputation of being a magician and diviner who had learned his black arts from Satan. Early in the seventeenth century a book was published in London entitled The famous historie of Fryer Bacon, containing the wonderful things that he did in his life, also the manner of his death, with the lives and deaths of the two conjurers, Bungey and Vandermast The book purports to tell the story of Bacon's life and magical exploits, including his creation of a brazen head that could talk and foretell the future and protect England from her enemies. After fashioning the “talking head” Bacon and Bungey waited for it to speak, but nothing happened for three weeks. Then “after some noyse the head spake these two words. ‘TIME IS’; and again after an interval, ‘TIME WAS’; and again, ‘TIME IS PAST,’ and therewith fell downe, and presently followed a terrible noyse, with strange flashes of fire.”