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ABSTRACT
Like most Enlightenment philosophers, Priestley acknowledges his debt to Newton. However, despite his mentor’s prohibition against “making hypotheses”, in the 1770s, he embarked on a surprising metaphysical epic that led him, the theologian and scientist, to develop in his Disquisitions a bold system that articulated materialism, necessity and Socinianism. This synthesis constitutes the originality of a thinker who wanted to reapprehend science, metaphysics and theology together at the very moment when their dispersion seemed inevitable (and to give them an educational and political extension). It is based on a monistic ontology to which Priestley did not hesitate to give the unexpected name of materialism, at the risk of a number of misunderstandings, while he claims, much to the dismay of Reid, to closely follow the method of Newton. This paper will focus on the relation between Priestley and Newton’s ambiguous inheritance. What is Priestley’s “science” made of? What is its relationship to Newton and his “rules”, to mathematics, to the theory of language, to the so-called “analysis and synthesis method”, to Boscovich? How important is his claim for hypotheses and metaphysics? If Priestley indeed was a Newtonian, he surely was an unorthodox one.
Notes on contributor
Pascal Taranto is full professor of philosophy at Aix-Marseille Université. He runs the Mixed Research Unit on philosophy and epistemology ‘Centre Gilles Gaston Granger’ in Aix (UMR 7304). He specializes in the philosophy of the Enlightenment and early modern British empiricism. He is the author of a monograph on Anthony Collins and many articles on Locke, Berkeley, Hume and Priestley.
Notes
1 Priestley credits Hartley and Boscovich (not least in his edition of the former), and mentions Collins approvingly in the Preface to Priestley, The Doctrine of Philosophical Necessity (XXX), among other places.
2 Cassirer, Die Philosophie der Aufklärung (1932), in Cassirer, Werke, vol. 15, 6.
3 Priestley, Disquisitions Relating to Matter and Spirit, 1–2.
4 For the history of these rules and their formulation, see Koyré, “Les regulae philosophandi”.
5 We may infer from Reid’s critical comments that he used the second edition as a reference text. Indeed, Reid does not mention rule IV and only speaks of the “three rules of Sir Isaac Newton”. Furthermore, not only does he quote the Latin text but he also reproaches Priestley for translating rule II by adding “as far as possible” as if it were a complete invention on Priestley’s part, whereas the text of the third Latin edition of 1726 clearly states “quatenus fieri potest”. Therefore, while Reid was only familiar with the second edition (1713), Priestley himself followed the third edition (1726), as he adds – in line with Newton’s text – the condition “as far as possible”, and translates, more accurately than Motte, regulae philosophandi as “rules of philosophyzing” rather than “rules of reasoning in philosophy”.
6 See Reid’s manuscript, in Wood, Thomas Reid on the Animate Creation, 192. The manuscripts of Reid, Observations, are available online on the Website of the University of Aberdeen, (MS 3061/1/2/3/4).
7 Less the term “materialist monism” seem problematic, given that Priestley is agnostic about the essence of God, I mean the following: Priestley, seeking primarily to demonstrate “the uniform composition of man” (i.e. monism against dualism) chose to use the term “matter” rather than “spirit”, despite being able to do so; see Priestley, Doctrine of Philosophical Necessity; Letter to Dr. Kenrick, 254. The case of God is perplexed and to be judged only by experience: if the design argument would fail, Priestley would be a kind of “Spinozist” (cf. Monboddo, Ancient Metaphysics, vol III, book I, 9–10; Monboddo, Ancient Metaphysics, vol II, viii), because signs of intelligent contrivance in nature are the only phaenomena that allows us to separate “God” (the unknown cause of known effects) from nature (see Priestley, Letters to a Philosophical Unbeliever).
8 Why are Newton’s third and fourth rules “the heart of the empiricism of natural philosophy”? In response to a reviewer’s query, I clarify that this is Reid’s interpretation of rule III (see quote below), and he is right as far as we think that “induction” means, from some peculiar experiences, to “conclude a quality to be common to all bodies whatsoever”, and that induction in this sense is the core of “empiricism”.
9 Newton’s comments on rule III, Principia book III (Mathematical Principles of Natural Philosophy, 796).
10 While Priestley argues that there are two fundamental powers, attraction and repulsion, these are, strictly speaking, two known effects of the same unknown power resulting from an unknown agency in matter. That’s why they are represented in Boscovich as a single function with a single curve alternating attraction and repulsion, though they can be generally spoken of as “two powers”.
11 While Priestley does not have his own, especially developed theory of superaddition, he refers in the Disquisitions to the debate involving Locke, Stillingfleet and Newton on the “superaddition” or “impression” of forces on matter by God. Priestley fully quotes Locke’s canonical text on superaddition (Locke, Essay, IV iii 6). His own position regarding the articulation of matter and thought is more determined and clearly stated than Locke’s. It is close to the conception of Hobbes, for whom thought comes from matter by virtue of its organisation. What God does is to organise matter into systems capable of producing thought on their own, through an internal causality that ultimately depends on an organisation engineered by creative intelligence (hence Priestley’s exclusive emphasis on the argument of design as proof of God’s existence), but does not claim his constant contribution to the production of the effect. It is no more an emergentism of self-organisation, as Collins envisioned (and which for the time is a real step towards atheistic materialism), than an animation of inert matter by the superaddition of a power. In the case of Locke and Newton, the question of the nature of matter is either left aside from the metaphysical point of view (substance is unknowable) or it remains ambiguous from an epistemic point of view (in accordance with the passive conception of corpuscular philosophy on the one hand, it seems on the other hand to carry an apparent, irreducible form of activity, except by the assumption of “fluids” and other “active principles”). Boscovich’s hypothesis will be for Priestley the opportunity to extricate himself from Locke’s (voluntarily?) indeterminate “superaddition”, and to put an end to the ambiguity of the “attributive” conception of power. It will make it possible to interpret impenetrability and solidity as the effect of a certain dynamic organisation of material points resulting from inherent powers of attraction and repulsion. This makes it conceivable that properties such as thought or perception coexist within this unknown substance with the usual properties recognised for matter (extension, vis inertiae).
12 Reid, Works, 59, in Wood, Thomas Reid on the Animate Creation, 72.
13 xliv.
14 Another theory, which may be inferred from the interpretation given by Wood, Thomas Reid on the Animate Creation, 73, note 52 – claiming that Priestley had knowledge of the rules through Boscovich – should be disregarded. Wood notes that in 1788, in his reading notes on Benedetto Stay’s (very) long poem on the Principia (Philosophia recentioris a Benedetto Stay … Versibus traditae libri X cum adnotationibus et supplementis P. Rogerii Josephi Boscovich S.J., Rome, 1755–1760 (Venice, 1744), see Reid MS 2131/3/i/p09). Reid states (57) that Boscovich and Stay both neglected to mention the important part “pluras causas … et verae sint”, that is the vera causa condition (see Wood, Thomas Reid on the Animate Creation, 172). One could therefore extrapolate from Reid’s comment that Priestley in fact adopted a “Boscovichian” version of the Rules. And yet Reid, inexplicably, is wrong on this point. On pages 56–57, note 1 of the poem, Boscovich comments on the verses by his Jesuit colleague and renders verbatim the second-edition version of the regulae (with the vera causa, but without the quatenus fieri potest), and the note on the preceding page cites and comments at length on rule III and the notion of induction. Schofield, for his part, suggests (Schofield, The Enlightened Joseph Priestley, 67) that Priestley may also have read these rules “for the first time” in the Mathematical elements of natural philosophy, confirm'd by experiments … by ‘s Gravesande (Vol. I, 3). And yet, while it is true that ‘s Gravesande only cites the first two rules, he does not omit the vera causa condition. This suggestion is therefore improbable.
15 Electricity, 429.
16 Electricity, 411.
17 One also encounters this kind of “Ockhamian” tropism in Boscovich, see Grmek, “La méthodologie de Boscovich”.
18 At the end of the second preface of Priestley, Disquisitions, he states his desire to move on to another subject after saying all he has to say, thus putting an end to his metaphysical efforts, to go back to what was the foremost goal of his entire life, a “true comprehension of the Scriptures”.
19 Golinski, Science as Public Culture, shows how Priestley, in the 1770s and 1780s, having been excluded from the main official institutions (but supported by his friends in the Lunar Society), focused all his energy on disseminating his experiments among as wide a public as possible, through writings and public lectures, in order to lift people from their state of ignorance, which was the source of their domination by a corrupt authority. The public, taking an interest in science, was invited to recreate experiments using simple, cheap instruments provided by Priestley himself, following a detailed, neutral and objective protocol. Although Priestley never tried to profit from his discoveries (others did so for him, such as a certain Mr Schweppe with carbonated water), he did accept patronage from the aristocracy, which was not entirely selfless. For the Lunar Society, see Schofield, The Lunar Society of Birmingham; Uglow, The Lunar Men.
20 Most “electricians” – such as Canton, Franklin, with the notable exception of Cavendish – did not concern themselves with mathematics.
21 See Schofield, “Joseph Priestley, the Theory of Oxidation and the Nature of Matter”.
22 While Priestley obviously provided a theory of matter as constituted by two fundamental powers (Priestley, Disquisitions, sect. 2), as a reviewer noted here, I mean “rigorous” in the sense of “operative” in experimental science, as the concept of mass is. Of course, there are metaphysical hypotheses about the nature of matter, the aim of which is nevertheless not to ground experimental science but to provide the monistic reduction of man with an “explanation” of facts and experiments that dualism cannot obtain.
23 The Newtonian Revolution, 53.
24 Haggerstone gave Priestley a copy of Euclid’s Elements, edited in 1678 by Isaac Barrow (Schofield, The Enlightenment of Joseph Priestley, 14). Priestley still had to study trigonometry and the calculation of fluxions. In the context of the Enlightenment, mathematics was often considered, on account of its exactitude and success, as a form of knowledge against which the certainty of theology appears rather weak. This kind of unfavourable comparison was often made by free thinkers. Berkeley wrote The Analyst in 1734 to counter an “infidel mathematician” whom Joseph Stock, his first biographer, identified as Edmund Halley, the astronomer and friend of Newton, on account of his reputation as an atheist (this identification is problematic, however; see Schaffer, “Halley’s Atheism and the End of The World”, note 58). Schofield presumed the mathematician in question was Colin Maclaurin; however, he had not yet published his Treatise of Fluxions (1742), which was partly motivated by Berkeley's critique of calculus. In any case, many mathematicians saw Berkeley Analyst, as a collective attack on their knowledge and faith, broadly targeting “Newton and his successors”, as evidenced by the title of the first reply he received: Cantabrigiensis (otherwise known as James Jurin, a well-known Cambridge scholar and physician), Geometry no Friend to Infidelity: or a Defence of Sir Isaac Newton and the British Mathematicians, 1734.
25 See Walker, “The Beginnings of the Scientific Career of Joseph Priestley”, 92. This certificate was signed by B. Franklin, J. Canton, S. Chandler and R. Price.
26 A matter with power to attract and repel must vary in volume according to its forces. The experiment showed that cold causes matter to contract while heat increases its volume. If we follow the Boscovichian model, with which Priestley was infatuated at the time he wrote the Disquisitions, “Priestley’s quantitative preoccupation with volumetric measurement is explained, for radial dimension was the operative parameter of that theory and measurement of volume change the most direct means of assigning value to the undefined variable” (Schofield, “Joseph Priestley, the Theory of Oxidation and the Nature of Matter”, 294).
27 This is the electrostatic law according to which force F exerted by charge Q on another charge q is directly proportional to the product of those two charges and inversely proportional to the distance of separation between them. Priestley expressed this in his History of Electricity. See Schofield, The Enlightened Joseph Priestley, 150f. Priestley gave, for the first time, a mathematical demonstration of the inverse square law of electric charges, from which a whole mathematical theory of static electricity would spring, but Priestley played no role in its subsequent development.
28 See Cohen, The Newtonian Revolution, first part: The Newtonian Revolution and the Newtonian Style, 62f.; Cohen, “Newton’s method and Newton’s style”.
29 Cohen, The Newtonian Revolution, 15.
30 Cohen, The Newtonian Revolution, 13f., and 133f.
31 On the use Maclaurin makes of Newton’s method and style, see Grabiner, “Newton, Maclaurin, and the Authority of Mathematics”.
32 Published in 1748, but begun in 1731, four years after Newton’s death, at the request of John Conduitt. The work was never finished.
33 Maclaurin, An Account of Sir Isaac Newton’s Philosophical Discoveries, 8–9.
34 Priestley, A Course of Lectures on Oratory and Criticism, Preface, i, ii.
35 ibid., 69.
36 A logic in the sense attributed to the term since Port-Royal; in other words, not a formal or symbolised theory but rather a rationalisation of ordinary language through an abstraction of its structure. The idea of “persuasion” as the ultimate goal of every argumentative speech is particularly important in the Rational Dissent movement, in which Priestley was prominent. Priestley introduced into the field of rhetoric some principles borrowed from Duncan, Elements of Logick. See Howell, Eighteenth Century British Logic and Rhetoric, 641.
37 Priestley, A Course of Lectures on Oratory and Criticism, 4.
38 ibid., 42.
39 ibid., 43.
40 ibid., 45.
41 Here a comparison may be drawn between Priestley and Lavoisier: for Priestley, science was a particular style of argumentative discourse, that is of the association of ideas; for Lavoisier, meanwhile, science was structured like a particular type of language; that is, like an immediate analysis of reality, based on specific measurements allowed by complex weighing equipment. Hence the importance given to nomenclature and “elements”. Lavoisier has assumed the power to name himself: oxygen, hydrogen, nitrogen, the name of reactions, compounds, which consumed the defeat of the theory of phlogistics and ousted tradition, fixing it for good in a bygone past. The battle over nomenclature revealed Priestley’s mistrust of words as much as the French chemists’ desire to ensure the success of their analysis by imposing a new grammar of Nature. See Lavoisier et al., Méthode de nomenclature chimique; Priestley, The Doctrine of Phlogiston established and that of the Composition of Water refuted, 3f.; McEvoy, “Priestley Responds to Lavoisier’s Nomenclature”.
42 The theme of a democratisation of science based on constant pedagogical effort also played a role in Priestley’s persistent fight against Lavoisier’s new chemical theory, whose verification required a complex, costly equipment that was out of the question for an amateur.
43 Cited in Schofield, The Enlightenment of Joseph Priestley, 239.
44 A Familiar Introduction … , Preface, xii.
45 McEvoy, “Continuity and Discontinuity in the Chemical Revolution”, 207.
46 Lavoisier, Méthode de nomenclature chimique, 298. The first pages develop the idea that ordinary languages, as Condillac believed (and to whom Lavoisier makes reference), were “real methods of analysis thanks to which we move from the known to the unknown and, up to a certain point, in the way of mathematicians,” such as in algebra (Lavoisier, Méthode de nomenclature chimique, 6). On the relationship between Condillac and Lavoisier, see Albury, “The Logic of Condillac and the Structure of French Chemical and Biological Theory”.
47 Heilbron, Electricity in the 17th and 18th Centuries, 500.
48 Kant believed the opposite, because for him metaphysics was an apodictic science based on a priori principles, like mathematics.
49 This point was established by Cohen, The Newtonian Revolution, in particular, in contrast with the traditional interpretations given by J. F. W. Herschel, K. Popper, N. R. Hanson and all those for whom Newton distinguished between good hypotheses (testable) and bad ones (“metaphysical”). See Worrall, “The Scope, Limits, and Distinctiveness of the Method of ‘Deduction from the Phenomena’: Some Lessons from Newton’s ‘Demonstrations’ in Optics”, 47f.
50 General Scholium.
51 Ak. V, 6, 7, see also Critique of Pure Reason, Ak. III 488, A745/B773.