La philosophie naturelle de Galilée. Essai sur les origines et la formation de la méchanique classique (review)

BOOK REVIEWS 341 in which the distinctions we attribute to reality are nothing but defects of human thinking. Hadot devotes an expository section to these "reversals of perspective": but one wonders why they are ignored when he is 'placing' Porphyry as a Neoplatonist philosopher. The subjectivism seems to me complementary to the telescoping of the hypostases. A second hesitation concerns Hadot's view--which did not of course start with him--of key concepts in Plotinus and Porphyry as transformations of Stoic concepts. Certainly the analogy between Neoplatonic procession and reversion and Stoic tonic, or centrifugal and centripetal, motion together with their philosophical functions i~ close; and even the 'pure act' of the One that is so indeterminate as not to be thinking or willing or anything rise may have had more affinity with an indeterminate Stoic 'motion' though I do not think this was as indeterminate as Hadot makes out--than with Aristotclian 'act'. But some other correspondences are open to question. To mention two: some claims about the influence of Stoic categories, of which we have little knowledge that is not coloured by Neoplatonic spectacles, and the claim (pp. 229-23!) that the hexis which the mind of a child acquires has a Stoic not an Aristotelian connotation in Porphyry's (?) treatise Ad Gaurum on the embryo. It is left unclear whether the relationship is meant as an historical and causal one or an abstract, conceptual one. This is perhaps deliberate and justifiable: it will stimulate, I hope, one among many other controversies which could not have been formulated so accurately nor so fairly before Hadot's work. A. C. LLOYD University of Liverpool, England La philosophie naturelle de Galil&e. Essai sur les origines et la formation de la mdcanique classique. By Maurice Clavelin. (Paris: Armand Colin, 1968. 504 pp., bibliog., index. 53.50 NF) Rather than tackling the broad subject its title promises, M. Clavelin's th~se de iettres sticks closely to the familiar business of characterizing Galileo's contributions to mechanics. It covers the ground opened by Duhem and cultivated by Maier, Moody, Clagett and especially Koyr~, whose Etudes galildennes seem to have served as its model. Clavelin's exposition of Aristotle's teachings about motion is very useful and perceptive, as he has labored to place them within the general body of Aristotelian natural philosophy. From Greece he leaps to the fourteenth century, and similar careful discussions of the well-known work of the calculators--who developed new ways of describing the accidents of motion--and of the Paris physicists, who introduced the doctrine of impetus into the ancient dynamics. Another jump and we arrive at the early work of Galileo, the so-called Juvenilia, which date from his twentieth year 0584), and the De Motu, written during his Paduan tenure 0589-1592). They testify to Galileo's familiarity with both the dynamics and the kinematics of the fourteenth century, and to his acceptance, as late as 1592, of much of the medieval approach to mechanics. But already in De Motu, and again in Le Mecaniche, written just after Galileo's translation to Padua, one finds the spirit of Archimedes mixed in with the peripatetic and medieval tradition. Clavelin expertly separates the different strands and emphasizes the fundamental importance of Galileo's analysis of traditional problems in statics, especially the balancing of weights on inclined planes, for the development of his dynamical ideas. Even the famous law of free fall might well have been discovered. 342 HISTORY OF PHILOSOPHY or at least initially justified, by arguments derived from the theory of bodies resting on slopes. Unfortunately Clavelin missed this capital point, which has recently received some attention in the British Journal for the History of Science.1 At Padua, where his experience and ambition greatly expanded, Galileo quickly moved beyond the clever but derivative work of his twenties. Clavelin arbitrarily selects 1602 as the 'end of the formative period,' largely on the strength of a letter Galileo wrote to Guido Ubaldo del Monte on November 29 of that year, announcing two new propositions in mechanics,z This periodization, which lumps together the Pisan and early Paduan years, unfortunately obscures a most important question, namely, how...