John of Dumbleton

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John of Dumbleton

(b, England; d. ca. 1349)

natural philosophy.

Virtually nothing is known of John of Dumbleton’s life. His name suggests that he may have come from the Gloucestershire village of Dumbleton. He is mentioned as a fellow of Merton College, Oxford, at various dates between 1338 and 1348, and in 1340 he was named as one of the original fellows of Queen’s College, but he could not have been there long

His work should be considered in relation to that of other fellows of Merton College, notably Bradwardine, Heytestbuty, and Richard Swineshead; but whereas the extant writings of these three deal only with particular problems of natural philosophy, Dumbleton’s huge Summa logicae et philosophiae naturalis attempts a fairly complete coverage of the topic, providing an invaluable source for opinions current at Oxford in his time. Of the nine extant parts of the Summa, the first deals with logic and the remaining eight with natural philosophy. These take their starting point in the Aristotelian writings and consider such subjects as matter and form: intension and remission of qualities; the definition and measure of motion; time; elements and mixtures; light; maxima and minima in physical to actions ; natural motions ; the first mover ; whether motion is eternal ; the generation of animals ; the soul ; and the senses . The promised tenth part, which was are to be reconciled with the Aristotelian interpretation of vision . He concluded that they are mere deal more fully with the rational soul and to consider the Platonic forms, is not extant, and quite probably Dumbleton died without having written it. In fact, there are indications throughout the treatise of a lack of careful editing.

Most of the subject matter of the Summa was, of course, commonplace in medieval discussions; but the techniques that Dumbleton employed were strongly influenced by the more mathematical scientific language for which Merton has become famous, and Dumbleton was always aware of the quantitative aspect of the problems he faced. In the first part of the Summa, for example, he considered at length the intension and remission of knowledge and doubt with respect to the evidence available and seemed to be exploring the possibility of a quantitative grammar of assent.

Although Dumbleton favored the Ockhamist definition of motion, this preference did not prevent him from applying to it a thoroughly mathematical treatment; by keeping a very close analogy between the speeds of motions and geometric straight lines, he was able to couch his discussion firmly within the language of the latitudes of forms. He accepted Bradwardine’s “law of motion” (which he regarded as being the view of Aristotle and Ibn Rushd) and devoted some space to expounding its consequences. His proof of the “Merton mean speed theorem” is interesting and in some ways reminiscent of the geometric method of exhaustion. He also considered how mathematical techniques could be applied to motions other than local motion. On the less mathematical side he tied his discussion of the continuance of projectile motion to his view that every body has a twofold natural motion: one upward or downward depending on its elementary composition, and another, more primitive motion arising from the desire of “every body. . . to be with another and follow it naturally lest a vacum be left.” He suggested that after a projectile has left the hand it follwos the air in front of it by virtue of the second type of natural motion.

One complete part of the Summa is devoted to “spiritual action” and more particularly to light, “through which spiritual action is made most apparent to us. This part is based solidly on Aristotle and Ibn Rushd, with the addition of a long mathematical discussion of the intensity of spiritual action. Geometrical optics does not appear here, but in discussing vision, Dumbleton considered how the “lines, triangles, and visual rays” used by writers on perspective are to be reconciled with the Aristotelian interpretation of vision. He concluded that they are mere fictions useful for calculating the position of the image when an object is viewed by reflection.

A full appreciation of Dumbleton’s work and its relation to that of his predecessors, contempories, and successors awaits much further research. As so often happens, we cannot easily ascertain how much of Dumbleton’s discussion is strictly original. He has, nevertheless, left us with much precious evidence relating to a period of intense intellectual activity, and the number of extant manuscript copies (at least twenty- one) testifies to the influence of his Summa.


I. Original Works. For a list of manuscript copies of the Summa logicae et philosophiae naturalis see J. A. Weisheipl, “Repertorium Mertonense” in Mediaeval Studies, 31 (1969), 174- 224. Dumbleton’s rather banal Compendium sex conclusionum and a small portion of the Summa have been edited in J. A Weisheipl, Early Fourteenth Century Physics of the Merton “School,” D. Phil. thesis (Oxford, 1956), pp. 392- 436.

II. Secondary Literature. On Dumbleton and his work, see M. Clagett, The Science of Mechanics in the Middle Ages (Madison, Wis- London, 1959) A. C Crombie Science (Oxoford, 1953); P. Duhem L e Systeme du monde, VII and VIII (Pairs, 1956- 1958); A. Maier, Zwei Grundprobleme der scholastischen Naturphilosophine (Vienna Leipzig, 1939- 1940; 3rd ed., Rome, 1968); An der Grenze von Scholastik und Naturwissenschaft (Essen, 1943; 2nd ed., Rome, 1952); Zwischen Philosophie und Mechanik (Rome, 1958); and J. A. Weisheipl, “The Place of John Dumbleton in the Merton School,” in Isis,50 (1959), 439-, 454; “Ockham and Some Mertonians,” in Mediaeval Studies, 30 (1968), 163- 213.

A. G. Molland