APPENDICES 1. THE PRECURSORS OF HUME (p. 58) It would seem that Hume had predecessors, or at the very least precursors, in the Middle Ages, in particular Robert Holkot in the twelfth century, about whom little is actually known (cf. IR 90, 342 [Loewenberg 87, 302]). As for Nicholas de Ultricuria [Nicolas of Autrecourt], who had previously been known only as an atomist and whose name has been suggested by Hastings RASHDALL ('Nicholas de Ultricuria, a Medieval Hume,' Proceedings of the Aristotelian Society 7 [1906-1907] 3 ff.), among the texts cited the only thing we see that really applies to this question consists of the following lines from Nicholas's Thesis 15: Quibuscunque acceptis, que possunt esse causa alicujus effectus, nescimus evidenter quod ad positionem eorum sequatur effectus positio ["Whatever conditions we take to be the cause of any effect, we do not evidently know that, those conditions being posited, it follows that the effect must be posited also" (Rashdall 10)], and this passage perhaps does not quite suffice to demonstrate the English author's claim. It is highly significant that both Robert and Nicolas professed atomistic opinions, and it is at least quite probable that, for these two aspects of their doctrines, they were closely linked to the Arab Mutakallimun, whom they probably knew through the resumes and refutations of Jewish thinkers, notably Maimonides, and who, in addition to a radical atomism, maintained the impossibility of any logical connection between cause and effect (see Isaac HUSIK, A History of Mediaeval Jewish Philosophy, New York: Macmillan, 1916, pp. xxi-xxii, xxvii, 249). During the Renaissance the distinction between causa and ratio was chiefly set forth by Giordano BRUNO (De la causa, Le Opere italiane, ed. Paolo de Lagarde, Gottingen: Dieterich, 1888, 1:230 [Cause, Principle and Unity, trans. Jack Lindsay, New York: International Publishers, 1962, pp. 79-80; Meyerson errs: Bruno is contrasting the terms causa and principio]), and there is no doubt a connection between his work and Galileo's statement on the impossibility of arriving "at complete knowledge of even a single thing in nature, be it ever so slight" (NORERO, 'Compte-rendu general du IVe 545 546 APPENDICES Congres international de philosophie,' Rev. de meta. 19 [1911] 626), and consequently of arriving at any real deduction of the natural phenomenon. But it must be noted that these words were probably aimed only at the exclusively logical procedures of the School and that his opinions about mathematical deduction were undoubtedly quite different (cf. pp. 375 ff. above). For the epoch immediately preceding that of Hume and in particular the relations that can be established between his thoughts on this question and those of Locke, Leibniz, Cordemoy and Malebranche, cf. IR 342-343 [Loewenberg 302-303]. 2. THE RESISTANCE TO LAVOISIER'S THEORY (p. 63) We know that none of Lavoisier's three great rivals, whose work had played such a powerful role in the destruction of phlogiston theory, ever converted to the new theory. Scheele, who was perhaps the most extraordi­ nary discoverer of experimental facts the history of science has ever known - FOURCROY, in his admirable historical account in the Encyclopedie methodique: Chimie, pharmacie et metallurgie, which is nothing but a long panegyric to the glory of Lavoisier, nevertheless observes, in speaking of the great Swede, that "no chemist has made so many discoveries, nor more important ones" (Enc. meth. 3:525), and Jean Baptiste DUMAS, a half century later, notes the almost incredible fact that in a single paper on manganese oxide Scheele discovers manganese, chlorine, baryta and probably oxygen as well (Ler;ons sur la philosophie chimique, 2nd ed., Paris: Gauthier-Villars, 1878, p. 103) - was the first to pass away, in 1786. Nevertheless he still witnessed the discovery of the decomposition of water, published by Lavoisier in 1784 but announced the preceding year at a session of the Academy of Sciences (Enc. meth. 3:444). It seems almost impossible, given the way in which scientific information was generally transmitted at that time and the frequency of the communications between Bergman and the French chemists on the one hand and between Bergman and Scheele on the other, that the latter did not immediately pick up some word of Lavoisier's experiments, which were attended by foreign scientists (like Blagden, for example, in June 1783; see Enc. meth. 3:444). But even quite independently of this consideration, it is curious to note Scheele's opinion of Lavoisier's ideas in 1784, eleven years after the latter had established the principle of the conservation of the weight of matter in the work on the Changement de l' eau en terre, ten years after the immortal Opuscules physiques et APPENDICES 547 chimiques which correctly explained the relations between carbonate of lime and quicklime, as well as between metals and their "calces," long after Lavoisier had completely set forth the foundations of his doctrine (between 1778 and 1780) and shown how useless and thus inadmissible it was to assume the existence of phlogiston: "Would it be so difficult to convince Lavoisier that his system of acids will not be to everyone's taste? Nitrous acid composed of pure air and nitrous air; aerial acid, of carbon and pure air; vitriolic acid, of sulfur and pure air; acidum sacchari, of sugar and pure air! Is this credible? I prefer to believe what the English say" (Carl Wilhelm SCHEELE, Letter to Bergman, 28 March 1783, Nachgelassene Briefe und Aufzeichnungen, ed. A. E. Nordenskiold, Stockholm: P. A. Norstedt & Soner, 1892, p. 364). Nitrous air (Salpeterluft) is what we call nitrogen dioxide; nitrous acid, nitric acid; pure air, oxygen; aerial acid, carbonic acid (the name Luftsiiure that Scheele uses had been given to it in 1774 by Bergman, replacing the earlier name of fIXed air or mephitic air; Lavoisier in 1777 called it chalky aeriform acid and finally, about 1783, acid of carbon; see Enc. meth. 3:432, 443, 476); acidum sacchari, oxalic acid. In referring to the English, Scheele was no doubt thinking of Cavendish and Priestley, but above all, it would seem, of Kirwan who, beginning in 1781, quite forcefully and ingeniously defended a doctrine according to which phlogiston was nothing other than inflammable air (that is, hydrogen), which was thus to be found in all combustible bodies. The idea won much support among the phlogiston theorists, and Scheele, as we see by the 1 February 1783 letter to Bergman (Nachgelassene Briefe 357, 360), strongly endorsed it. Cavendish and Priestley lived on for many years. After a while, Cavendish stopped publicly defending phlogiston theory. What is more, he stopped doing chemistry (turning to the study of electricity, where he also made important discoveries, which he completely neglected to publish and which only became known long after his death). Perhaps his decision was not unrelated to the evolution in the chemists' prevailing opinion of the new ideas, which he found so antipathetic. At any rate, he never adopted the antiphlogiston theory, and all that he conceded toward the end of his life is that "most of the phenomena of nature seem to be capable of being explained as well, or almost as well, by Lavoisier's views as by the generally accepted principles of phlogiston theory." Priestley fought Lavoisier's theory to his last breath, so to speak. As we know, Priestley was a man as remarkable for the loftiness and strength of 548 APPENDICES his character as for the high value of his scientific intelligence. He was an enthusiastic supporter of the French Revolution, so unpopular in England at that time; in his Letters to the Right Honorable Edmund Burke (Birmingham: T. Pearson / J. Johnson) in 1791, he vigorously defended it against the impassioned attacks of this great orator. The same year, when it become known in Birmingham (where Priestley served as minister to a nonconformist community) that a few people had dared assemble to celebrate the anniversary of the fall of the Bastille, Priestley's house was ransacked and burned by the incensed crowd. The great scientist lost his entire fortune, most significantly some infinitely precious scientific instruments (the Academy of Sciences in Paris extended its sympathy to him on this occasion and Priestley, already honored with the title of French citizen, was in 1792 elected a representative to the Convention from the department of the Orne, a mandate he declined; he had explicitly accepted the title of citizen, and one of his sons, who lived as a planter in Louisiana and died there in 1835, retained the title). Rather than yield, Priestley emigrated to America, where he spent the last years of his life. He defended his scientific ideas with equal ardor. "His perseverance in the battle for his basic ideas was extraordinary," said Cuvier in the beautiful Eulogy he delivered shortly after the death of the scientist. "Impassively he watched their ablest defenders move one by one into the enemy camp, and when at last even Kirwan had repudiated phlogiston, Priestley, standing alone on the battlefield, launched yet another challenge in a paper addressed to the leading French chemists" (Memo ires de l'Institut des Sciences, Lettres et Arts: Sciences mathematiques et physiques, 1806, 6:42-43). This challenge is the Considerations on the Doctrine of Phlogiston published in 1796. In spite of the fact that his adversaries seem to have won the acclaim of the scientific world, he feels so sure he is right that he sarcastically enjoins them: "Do not treat me like Robespierre. Bear with a small Vendee in chemistry! Answer me, persuade me, and don't abuse your power" (DUMAS 125). The chemist Adet, who had worked in Lavo~ier's laboratory and was cofounder with him of the Annales de Chimie, of which he was editorial secretary, was at that moment serving as French ambassador to the United States.