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Marliani, Giovanni


(b. Milan, Italy, early fifteenth century: d. Milan, late 1483)

physics, Mechanics, medicine.

There is little information on Marliani’s early life. Born into a patrician family, he probably studied arts and medicine at Pavia University. In 1440 he was elected to the College of Physicians at Milan: it seems that he had received his doctorate by then, or certainly before 1442. From 1441 to 1447 Marliani taught natural philosophy and “astrologia” at Pavia, and lectured on the physics of Bradwardine and Albert of Saxony. Under the short-lived Ambrosian Republic, he left Pavia for the University of Milan (1447–1450), where he taught medicine. He was also appointed to civic office. Following the collapse of the Ambrosian Republic, Marliani returned to Pavia, where he added medicine to his previous lectureships, eventually acquiring (1469) the chair of medical theory. His salaries testify to a successful career: in 1441 Marliani earned 40 florins a year; in 1447, 200 florins; in 1463, 500 florins, plus, by secret arrangement with Duke Francesco I Sforza, an additional 150 florins. Later a special chair was set up for the Marliabu family, to be held first by Giovanni’s son, Paolo, in 1483. Two other sons, Girolamo and Pietro, also lectured at the university. The fortune of the family was sealed with Marliani’s appointment (probably in 1472) as court physician to Galeazzo Maria Sforza. He also enjoyed the favor of the latter’s successor, Gian Galeazzo.

Despite his strongly Scholastic views, Marliani was well regarded by humanists of the time. Pico della Mirandola called him the greatest mathematician of the age, and Francesco Filelfo and Marliani corresponded on medical and Scholastic matters. Giorgio Valla, who studied medicine and mathematics under Marliani at Pavia, translated the Problemata of Alexander of Aphrodisias at the urging of his teacher. Valla stated that Marliani owned a copy of Jacobus Cremonensis’ translation of Archimedes, but the sole extant mathematical work by Marliani is on common fractions and shows little originality or knowledge of Greek mathematics. Valla’s later work, however, abandoned the Scholastic physics of his teacher in favor of classical mathematics. Most Renaissance humanists and mathematicians shared Valla’s preference.

Three works by Marliani deal with heat in a strongly Aristotelian fashion. The heating or cooling action is regarded as a special case of motion and thus subject to Aristotle’s mistaken law of motion. In the early treatise De reactione, for instance, reaction (meaning the capacity of an agent to be affected by its patient) is analyzed in terms of active and resistive powers, as though it were motion. Although Marliani admits his debt to Jacopo da Forli and others, he systematically rejects many of these predecessors” arguments in favor of some rather tortuous arguments of his own. (His criticisms soon involved Marliani in a polemic with Gaetano da Thiene.) Two main points of interest appear in the De reactione, although neither is original. These are Marliani’s distinction between intensity of heat (temperature) and its extension (quantity of heat) and his use of a numerical scale to represent the intensity. This scale consists of eight degrees of calidity and its coextensive frigidity (F° = 8 – C°) The Marliani scale should not, perhaps, be taken as a forerunner of the thermometric scale, since it depends conceptually upon an Aristotelian qualitative distinction between heat and cold.

The Disputatio cum Joanne de Arculis discusses the reduction of hot water (that is, whether hot water is cooled by an intrinsic tendency or an extrinsic agent, such as its container). Marliani again applies his Aristotelian principle relating action and resistance to the quantity of heat and cold present. In contrast with his Avicennist opponent Giovanni Arcolani of Verona, who argues for intrinsic reduction, Marliani maintains that at any temperature, hot and cold components of the water are in equilibrium and thus cannot act upon one another. Hence, the cooling agent must be external. He also concludes that the shapes of the agent and the patient, and their distance apart, are factors in a heat action.

De caliditate corporum humanorum combines Marliani’s knowledge of medicine and physics. Distinguishing between heat intensity (temperature) and its extension (the quantity of “natural” heat produced by the body), Marliani concludes that the human body, while increasing its natural heat in the winter, maintains a more or less constant temperature through most of its parts. Nevertheless, he still feels obliged (despite a youthful repudiation) to accept the notion of antiperistasis (the increase of intensity when a body is suddenly surrounded by its contrary quality), which underlay the arguments for a varying body temperature.

Marliani’s writings on mechanics center on two main problems of Scholastic physics. In the Probatio calculatoris the kinematic mean-speed theorem of accelerated motion is outlined with some clear proofs. Of more significance is the De proportione motuum, designed to solve a paradox in Aristotle’s law of motion. The Aristotelian law held velocity to be proportional to the ratio of the moving power to the resistance. A paradox arose when the moving power was equal to the resistance. Obviously no motion should then occur, but the ratio in the law gave a positive value to the velocity in this case. Bradwardine’s law tried to eliminate the paradox by stating that the “proportions of velocities in motions follow the proportion of the power of the motor, to the power of the thing moved.” Using the proportion of proportions calls for a geometrical increase in the ratio of force to resistance. Bradwardine, however, used terms which can denote either an arithmetical or geometrical increase—for instance, “dupla,” to mean “deouble” or “squared.” Misled by this ambiguous terminology to assume that Bradwardine had fallen into the same trap as Aristotle, Marliani severely condemned the former and advanced his own law that velocity is proportional to the excess of the motor power over the resistance. Nevertheless, Bradwardine’s law remained acceptable to most Renaissance Aristotelian philosophers.

Marliani’s career and works suggest that he was a competent Scholastic physicist and an adept publicist of the calculatores and French Scholastics in Italy. Influential among philosophers (his De reactione was later discussed by Pietro Pomponazzi), Marliani seems to have stayed largely outside the mainstream of Italian Renaissance mathematics. Much of his great reputation seems also to have rested on his position as physician to the Sforzas.


I. Orgirinal Works. Unless otherwise noted, Marliani’s works were printed at Pavia in 2 vols. in 1482. The dates of composition are in parentheses. The writings are Tractatus de reactione (1448); In defensionem Tractatus de reactione (against Gaetano da Thiene, 1454–1456); “Annotationes in librum de instanti Petri Mantuani,” unpub. work in Biblioteca Vaticana, MS Vat. Lat. 2225 (see Thorndike, below); Probatio cuiusdam sententiae calculatoris de motu locali (1460); Disputatio cum Joanne de Arculis (1461); Difficultates missae Philippo Adiute Veneto (before 1464); “Algorismus de minutiis” (before 1464), unpub. MSS in Bibliothéque Nationale, Paris, MS N.A.L. 761, and Biblioteca Ambrosiana, Milan, MS A.203 infra; Questio de proportione motuum in velocitate (1464); and Questio de caliditate corporum humanorum (1472).

II. Secondary Literature, For mentions of Marliani, see Pico della Mirandola, Disputationes adversus astrologiam divinatricem, E. Garin ed. (Florence, 1946), pp. 632–633; and J. L. Heiberg, “Beiträge zur Geschichte Georg Valla’s und seiner Bibliothek,” in Zentralblatt für Bibliothekswesen, supp. 16 (1896), 11–12, 85. An excellent treatment is Marshall Clagett, Giovanni Marliani and Late Medieval Physics (New York, 1941); see also his “Note on the Tractatus physici Falsely Attributed to Giovanni Marliani,” in Isis, 34 (1942), 168, appended to D. B. Durand’s review of the book. see also A. Maier, Die Vorläufer Galileis im 14. Jahrhundert (Rome, 1949), pp. 107–110; and the inaccurate pages in p. Duhem, Études sur Léonard de Vinci, III (Paris, 1913), 497–500. Two letters to Marliani are in Francesco Filelfo, Epistolarum (Venice, 1502), fols. 152v, 184v.

For MSS see Lynn Thorndike, “Some Medieval and Renaissance Manuscripts on Physics,” Proceedings of the American philosophical Society, 104 (1960), 188–201, esp. 195; and Lynn Thorndike and pearl Kibre, A Catalogue of Incipits of Medieval Scientific Writings in Latin, 2nd ed. (London, 1963), index “Marliani.”

For Scholastic science in fifteenth-century Italy, see Carlo Dionisotti, “Ermolao Barbaro e la fortuna di Suiseth,” in Medioevo e Rinasciemento. Studi in onore di Bruno Nardi (Florence, 1955), I, 217–253, eps. 230–231.

Paul Lawrence Rose

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