Dietrich von Freiberg was a German theologian, clergyman and physicist. As a monk, he was a member of the Dominican Order, where he held high offices. His works include numerous philosophical, theological and scientific writings, and they focuse on questions of ontology, epistemology, cosmology, anthropology, and the theory of time.
Background
Dietrich von Freiberg was born c. 1250 in Freiberg, Germany. In Latin his name is written Theodoricus Teutonicus de Vriberg. This has been anglicized as Theodoric of Freiberg and rendered into French as Thierry de Fribourg. Which of the many Freibergs or Freiburgs is the place of his birth is not known for certain; Krebs regards Freiberg in Saxony as the most likely.
Education
Freiberg studied at the University of Paris about 1275-1277. He earned the title of master of theology at St. Jacques in Paris before 1303.
Freiberg is sometimes cited as a disciple of Albertus Magnus; although he is in Albert’s tradition, there is no direct evidence that Albert actually taught him.
Career
Freiberg entered the Dominican order (province of Teutonia), was named provincial of Teutonia in 1293 and was appointed vicar provincial again in 1310. In 1304 he was present at the general chapter of his order held in Toulouse, where he was requested by the master general, Aymeric de Plaisance, to put his investigations on the rainbow into writing.
Freiberg’s place in the history of science is assured by his De iride el radialibus impressionibus (“On the Rainbow and ‘Radiant Impressions,’ ” i.e., phenomena produced in the upper atmosphere by radiation from the sun or other heavenly body), a treatise composed shortly after 1304 and running to over 170 pages in the printed edition (1914).
In an age when scientific experimentation was practically unknown, he investigated thoroughly the paths of light rays through crystalline spheres and flasks filled with water; and he deduced therefrom the main elements of a theory of the rainbow that was to be perfected only centuries later by Descartes and Newton. He also worked out a novel theory of the elements that was related to his optical researches and wrote on the heavenly bodies, although the latter of these contributions is more the work of a philosopher than of a physical scientist in the modern sense.
His work represents a great breakthrough in geometrical optics, and yet a simple error in geometry prevented him from giving a correct quantitative theory of the rainbow. In essence, this came about through his using the “meteorological sphere” of Aristotle as his basic frame of reference.
A most interesting part of Freiberg’s De iride - which led him to compose a companion treatise, De coloribus (“On Colors”) - is his ingenious but unsuccessful attempt to explain how the colors of the rainbow are generated. It is in these portions of his work, generally passed over rapidly by historians of science, that one can discern in his procedure an interplay between theory and experiment foreshadowing the characteristic methodology of modern science. He was confident that he had discovered the true “causes” of the bows, and thus he proposed his geometrical explanations of their formation as apodictic demonstrations in the Aristotelian mode. He never was convinced, on the other hand, that he had gotten to the “causes” of radiant color; and thus he had to content himself with the search for the “principles” of such color formation.
In this search he fell back on a Peripatetic argument involving “contraries,” the classical paradigm of dialectical reasoning. He used as his analogy the medieval theory of the elements, according to which the four basic contrary qualities of hot-cold and wet-dry, in proper combination, account for the generation of the four elements (fire, air, water, and earth). To employ this, he had first to establish that there are four colors in the spectrum-and this contrary to Aristotle and almost all of his contemporaries, who held that there are only three. His inductive argument here is superb, and the way in which he employs observation and experiment to overthrow the authority of Aristotle would delight any seventeenth-century thinker.
Freiberg was less fortunate in explaining the origin of colors in terms of his two “formal principles” (clear-obscure) and two “material principles” (bounded-unbounded). He did, however, contrive a whole series of experiments, leading to various ad hoc assumptions, in his attempt to verify the explanation he proposed. Yet it seems that he was never quite sure of this, and in fact a quite different approach was needed to solve his problem - it was provided by Sir Isaac Newton.
Possibly because of an interest in the elements aroused by his optical studies, Freiberg wrote opuscula entitled De dementis corporum naturalium (“On the Elements of Natural Bodies”), De miscibilibus in mixto (“On Elements in the Compound”), and De luce et eius origine (“On Light and Its Production”). These are neither mathematical nor experimental, but they do shed light on his theories of the structure of matter and his analysis of gravitational motion. He also composed treatises relating to astronomy, De corporibus celestibus quoad naturam eorum corporalem (“On Heavenly Bodies With Regard to Their Corporeal Nature”) and De intelligenciis et motoribus celorum (“On Intelligences and the Movers of the Heavens”); the latter has been analyzed by Duhem, who sees it as a retrogression from the astronomical contributions of Albertus Magnus.
He is also credited with having influenced the development of speculative mysticism as it was to be taught by Meister Eckhart and Johannes Tauler, both of whom were German Dominicans.
Religion
Freiberg was a member of the Dominican order.
Views
Freiberg is best characterized as an eclectic, although he generally followed the Aristotelian tradition in philosophy and the Augustinian-Neoplatonic tradition in theology. He opposed Thomas Aquinas on key metaphysical theses, including the real distinction between essence and existence. Crombie argues for an influence of Robert Grosseteste on Freiberg from similarities in their optics, but the evidence is meager; he certainly rejected the “metaphysics of light” by Grosseteste and Roger Bacon, and he did not subscribe to the mathematicist view of nature that was common in the Oxford school. Again, his interest in Neoplatonism was more theological and mystical than philosophical.
The mathematical basis for Freiberg’s reasoning stems from the perspectiva, or geometrical optics, of the Schoolmen and of Arabs such as Ibn al-Haytham (Alhazen); and his measurements are those of medieval astronomy, based on the primitive trigonometry of Ptolemy’s Almagest. He does not propose a “theory” in the technical sense, although there is a hypothetical element in his thinking that can be disengaged on careful reading. Rather, he explicitly locates his own method in the framework of Aristotle’s Posterior Analytics, which puts him on the search for the causes of the rainbow, through discovery of which he hopes to be able to deduce all of the rainbow’s properties. This demonstrative ideal of Aristotelian science, it may be noted, did not exclude the use of dialectical (or conjectural) reasoning by its practitioner, although later Scholastics have tended to overlook the latter element.
Freiberg’s empiricism also derives from the Aristotelian tradition, even though portions of his theory of knowledge are markedly Augustinian. His optics makes implicit use of a method of resolution and composition that was already known to Grosseteste and that was to be refined considerably by the Averroist Aristotelians at Padua, who educated the young Galileo in its use.
He was not content merely to observe nature but attempted to duplicate nature’s operation by isolating the component factors of that operation in a way that permitted their study at close range. Most of his predecessors had regarded the rain cloud as an effective agent in the production of the rainbow; even when they suspected that the individual drop played a significant role, as did Albertus Magnus, they saw no way of isolating it from the collection that produced the bow. When, for example, they compared the colors of the bow with the spectrum resulting from the sun’s rays passing through a spherical flask of water, they tended to equate the flask with a cloud or with a collection of drops. It was Freiberg who apparently was the first to see “that a globe of water can be thought of, not as a diminutive spherical cloud, but as a magnified raindrop.” This insight, coupled with the recognition that the bow is simply the aggregate of effects produced by many individual drops, ultimately led him to the first essentially correct explanation of the primary and secondary bows.