. We begin with a distinction between what the medievals called “science” (scientia) and what, if anything, corresponds to our modern understanding of the term. Scientia, following Aristotle meant systematic knowledge, organized through principles, so that philosophy and theology were “sciences” along with physics and mathematics. Prior to the 12th century, “science” meant the Quadrivium (arithmetic, geometry, music, and astronomy) and the Trivium (grammar, rhetoric, and logic), which together comprised the notion of Liberal Arts. In the 12th and 13th centuries, translations into Latin from the Arabic (by Gerard of Cremona [d. 1187]) and from the Greek (by William of Moerbeke [d. ca. 1286]) brought an explosion of “new” knowledge, information, and disciplines into the mainstream of medieval intellectual life: Aristotle, Euclid, Alkindi, Avicenna, Averroes, Al Farabi, Galen, Alexander of Aphrodisias, and Proclus, among others. These texts provided both authoritative sources and the impetus for extension and expansion of the “sciences of nature” (called “natural philosophy” [philosophia naturalis or physica]), While the whole is called “philosophy” (from the Greek, [love]] and [wisdom]), classification of the parts differed. Hugh of Saint-Victor (d. 1141) divided philosophy into theoretical, practical, mechanical, and logical. He listed medicine among the mechanical arts and declared it a suitable occupation for manually adept members of the lower classes. Being concerned with a product, health, which it borrows from nature, disqualifies medical knowledge from inclusion among the higher, more speculative branches of knowledge. Dominicus Gundissalinus (fl. 1140) divided philosophy into two parts: theoretical and practical. The first is further divided into physical science, mathematics, and the highest speculative science, known variously as theology, first philosophy, or metaphysics. The second is divided into political science, family ordering, and ethical or moral science. Gundisalvo includes medicine among the physical sciences.
When we look for areas of knowledge cognate with our modern understanding of science, we find mathematics, physics (including theory of weight, motion, kinetics, dynamics, magnetism, optics), astronomy and astrology, chemistry and alchemy, geography, oceanography, zoology and botany, and medicine (including anatomy, physiology, and pharmacology; medical diagnosis, treatment, and surgery). (The inclusion of astrology and alchemy in the list suggests the affinity that medieval science had to “magic.”) There is also great concern to provide a theoretical account of the structure and dynamics of the universe (cosmology) as well as some attempts to reflect upon methods.
The generally accepted cosmology rested on the assumption of an immobile earth at the center of the universe, with the stars and planets revolving about the earth within concentric spheres—as proposed by Ptolemy (fl. A.D. 127–51) and systematized in Aristotle’s physical treatises. Arguments on behalf of a rotating earth were known to the Medievals (e.g., Ptolemy himself, Jean Buridan [b. ca. 1300] and Nicole Oresme [b. ca. 1320/25]) but were not accepted as conclusive. Even in rejecting those arguments, however, both Buridan and Oresme recognized that, on the assumption of a moving earth, the heavenly phenomena would appear to us just as they do on the assumption of a stationary earth.
This cosmology provided the theoretical basis for astrology. Actually, “astronomy” and “astrology” were often used interchangeably; for example, Albert the Great (ca. 1200–1280) says there are two parts to astronomy, the second of which we would be inclined to call “astrology.” In general, “astronomy 1” is the science of the stars, the reasons for their relations to one another and to the earth; “astronomy 2” (astrology) is the science of describing the position of the stars for obtaining “a knowledge of the times.” The basis for the latter is the causal influences exercised by the former throughout the concentric spheres of the universe down to the region under the moon. Astrological judgments may seem to contradict human free will inasmuch as they seem to place in the hands of the astrologer (astronomer) who understands the causal connection of the movements of heavenly bodies to the events in the sublunar world, a knowledge of necessity and determinism that appears to be at odds with human freedom. But the apparent contradiction, Albert maintains, is not real. Astrological knowledge concerns not human actions directly but dispositions to actions that are always subject to whether the act will or will not actually be done. Persons remain masters of their fate by using their intellect. A person can avert much evil from the effects of the operations of the stars if he knows the influence to be exerted and can prepare to receive it. Choosing the favorable hour expresses both the astrological influence and human freedom. On the other hand, casting horoscopes, although not condemned by Albert, is recognized as emphasizing the potential conflict between astrological horoscopes (as, e.g., when the length of a life is predicted from the constellations) and free will.
As far as methods were concerned, Robert Grosseteste (b. ca. 1168) may serve as a good example. Grosseteste based his approach to scientific knowledge on Aristotle’s Posterior Analytics: a two-stage process. Beginning with an observed fact, the scientist “resolves” the fact into the principles or elements that constitute it; the second stage consists of “composing,” that is, reconstructing the fact on the basis of its “reasons” or “causes.” This approach assumed both a uniformity in nature and a principle of economy that chose between competing explanations on grounds of needing the fewer number of suppositions. Because of these “extra-demonstrative” assumptions, Grosseteste’s approach yielded probable rather than strictly scientific knowledge of the natural world, since the observed facts would be deduced from more than one explanatory theory without contradiction. In providing scientific knowledge of the heavens or of the behavior of light in optics, Grosseteste recognized that he was providing the formal cause (from the four-cause explanatory structure of explanation provided by Aristotle: formal, material, efficient, and final causes), but he could not provide the material or efficient causes—nor, within natural science—the final cause either. The formal cause could be deduced mathematically (say, geometric epicycles and eccentrics in astronomy); but the material and efficient causes required knowledge of natures—the subject matter of other, higher sciences. Because of his metaphysical theory that light was the basic nature of physical reality, Grosseteste regarded optics as the foundation of physical science; but optics required the mathematics of lines, figures, and angles. Grosseteste was, thus, one of the first to link mathematics directly to the study of natural phenomena beyond the movements of the heavenly bodies.
Grosseteste wrote Commentaries on the Physics and the Posterior Analytics of Aristotle and produced some original treaties on optics. Perhaps no one, however, better expresses the impact of the full corpus of Aristotle’s works (and their Arabic commentaries) made available by the 12th- and 13th-century translations than Albert the Great. His voluminous writings include detailed commentaries on Aristotle’s physical and biological treatises, to which he added extensive examples of his own observations of flora and fauna gained on his travels on foot in Germany, France, and Italy. What characterized Albert’s approach to science and set him apart from many of his contemporaries was his continuous insistence on his own observations and on the need to return to what in Latin is experimentum. The term “experiment” cannot be understood in the modern sense. More often than not, the term indicates a careful, scrutinizing process of observing, describing, and classifying. At the same time, natural magic was considered a branch of science: the science that dealt with “occult virtues” (or hidden powers) within nature. God acts through natural causes in the case of natural phenomena, says Albert; and while we would not presume to investigate the causes of the divine will, we are free to investigate—in detail and specifically—the natural causes that are instruments of the divine will. It is in the spirit of what Albert reads in Aristotle (and in pseudo-Aristotelian texts) that he seeks concrete, specific, detailed, accurate knowledge of everything in nature. There are many powers of stones and plants that are learned by experience, and magicians, as well as natural philosophers, investigating these powers, work wonders with them.
Albert’s reputation for magic was probably based on two things: 1) there are many references to magic scattered throughout Albert’s writings, many of them expressing approval, and some include explicit treatments of the special case of magic, astrology; and 2) the prodigious accumulation of factual (and reportedly factual) knowledge of the natural world, including the medicinal powers of herbs, the folklore about the powers of stones and minerals together with theories of the structure of natural substances and the organization of the universe: all contributed to a Faustian characterization of this one man of the 13th century to be called “Great.”
The association of science and the magical arts is evidenced in several ways. The Libellus de alchimia, for example, lists several (“scientific”?) precepts for the alchemist to follow:
1) the alchemist/scientist should work silently and secretly; if many know what he is doing, the secret will not be kept and when it is divulged, it will be repeated with error; 2) the scientist should have a laboratory—a special house away from the sight of others in which to carry out his procedures; 3) the scientist must observe the time and the seasons; 4) the scientist must be sedulous, persevering, untiring—a constant worker; if he begins and does not persevere, he will lose both materials and time; 5) in all procedures, the scientist must have and follow a protocol; 6) all vessels should be made of glass; 7) the scientist should stay away from administrators; if you are committed to your work, they will bother you with questions about how you are coming and when will you be finished, and if you take too long they will regard your work as trifling and you will experience great dissatisfaction. Of course, if you do not succeed, you will be humiliated; if you do succeed, they will give you something else to do; 8) finally, the scientist should have plenty of money.
Medieval science, then, was comprehensive and holistic, both in the sense of embracing all areas of human knowledge and in the sense of a hierarchy of interrelated knowledges. It was profoundly aware of and deferential to the great minds and intellectual traditions of preceding ages, pagan as well as religious, without mistaking authority for reasons. “Science” only slowly differentiated itself from “magic,” since both concerned natural phenomena. Mathematics provided a deductive discipline, a source of theoretical explanation of bodies in motion, and the beginnings of what would become an essential constituent of later science.
meant systematic knowledge, organized through principles, so that philosophy and theology were “sciences” along with physics and mathematics. Prior to the 12th century, “science” meant the Quadrivium (arithmetic, geometry, music, and astronomy) and the Trivium (grammar, rhetoric, and logic), which together comprised the notion of Liberal Arts. In the 12th and 13th centuries, translations into Latin from the Arabic (by Gerard of Cremona [d. 1187]) and from the Greek (by William of Moerbeke [d. ca. 1286]) brought an explosion of “new” knowledge, information, and disciplines into the mainstream of medieval intellectual life: Aristotle, Euclid, Alkindi, Avicenna, Averroes, Al Farabi, Galen, Alexander of Aphrodisias, and Proclus, among others. These texts provided both authoritative sources and the impetus for extension and expansion of the “sciences of nature” (called “natural philosophy” [philosophia naturalis or physica]), While the whole is called “philosophy” (from the Greek, 
[love]] and 
[wisdom]), classification of the parts differed. Hugh of Saint-Victor (d. 1141) divided philosophy into theoretical, practical, mechanical, and logical. He listed medicine among the mechanical arts and declared it a suitable occupation for manually adept members of the lower classes. Being concerned with a product, health, which it borrows from nature, disqualifies medical knowledge from inclusion among the higher, more speculative branches of knowledge. Dominicus Gundissalinus (fl. 1140) divided philosophy into two parts: theoretical and practical. The first is further divided into physical science, mathematics, and the highest speculative science, known variously as theology, first philosophy, or metaphysics. The second is divided into political science, family ordering, and ethical or moral science. Gundisalvo includes medicine among the physical sciences. 
