Hume’s Attack on Newton’s Philosophy
Abstract
This paper argues that major elements of Hume’s philosophy are directed against Newton’s philosophy. Hume reverses Newton’s epistemology by asserting the supremacy of the “science of man.” For Hume it can attain “proof,” while much of the physical sciences must do with mere “probability.” Moreover, Hume’s account of causation is designed to undercut the reductionist bias of natural philosophy; in Hume’s program there is no need to look for physical causes underlying the phenomena. Furthermore, while Hume’s “rules by which to judge of causes and effects” are, with the exception of rule 7, modeled on Newton’s Rules of Reasoning, Hume does not replicate Newton’s rule 4, which contains Newton’s most important reflections on ontology and methodology. This allows Hume to claim that the natural sciences that go beyond common life should be treated in instrumentalist fashion. The paper ends with a discussion of the subtitle of the Treatise, “Attempt to Introduce the Experimental Method of Reasoning into Moral Subjects,” which signals Hume’s methodological commitment to Boyle’s experimental philosophy and not Newton’s mathematical natural philosophy.
Hume’s Attack on Newton’s Philosophy
I Introduction and Summary
In this paper, I argue that major elements of Hume’s philosophy are directed against Newton’s philosophy. There is little doubt that Hume was very interested in and admired Newton’s contribution to natural philosophy.[i] Nevertheless, it is well known that Hume attacked the (inductive) argument from design, which seemed to follow from the success of Newton’s system.[ii] But in arguing that the thrust of Hume’s epistemology is an attack on the supremacy of Newtonian natural philosophy in a general sense, I go against the grain of much Hume scholarship, which makes many obligatory references to Newtonians element in Hume.[iii] Some scholars have argued that Hume’s “rules,” (Treatise, 1.3.15), his “Experiments” and “Anatomy” (Treatise, 1.4.6.23), and his method of investigation, especially in Books II and III of the Treatise, are modeled on Newton’s Rules of Reasoning or inspired by Newtonian natural philosophy.[iv] Also, many scholars have noted that Hume derived metaphors from Newtonian natural philosophy. For example, Hume talks of an “attraction” in the “mental world” on a par with that in the “natural world.” (1.1.4.6) In this paper, my claim is not that Newton did not figure importantly in Hume’s philosophy, but, instead, that Hume’s project is more hostile to Newton’s achievements than many of his Positivist or Naturalist interpreters have realized, even leaving aside issues regarding nature of Hume’s skepticism.[v]
This essay consists of six substantial sections. In section II, I discuss Hume’s reversal of Newton’s epistemology. For in the Opticks, Newton claims that natural philosophy should be foundation for other sciences, while in the “Introduction” to the Treatise Hume asserts the supremacy of the “science of man.”[vi] This is why for Hume the social sciences can attain the high epistemic status of “proof,” while much of the physical sciences must do with mere “probability” (III). Moreover, Hume’s account of causation is designed to undercut the reductionist bias of natural philosophy (IV); in Hume’s program there is no need to look for physical causes underlying the phenomena.[vii] Higher level causation can provide satisfying explanations. Furthermore, while it should be granted that Hume’s “rules by which to judge of causes and effects” are, with the exception of rule 7, modeled on Newton’s Rules of Reasoning (Principia, Book III), Hume does not replicate Newton’s rule 4, which contains Newton’s most important reflections on ontology and methodology. (V) This omission, together with the arguments from sections III-V, allows Hume to claim – following Berkeley – that the natural sciences go beyond common life should be reinterpreted and treated in instrumentalist fashion (VI). I end with a brief discussion of the meaning of the subtitle of the Treatise, “Attempt to Introduce the Experimental Method of Reasoning into Moral Subjects,” which may be thought to show Hume’s debt to Newton. I argue, however, that it signals Hume’s methodological commitment to Boyle’s experimental philosophy and not Newton’s mathematical natural philosophy (VII). I end with a thought on the larger significance of Hume’s attack on Newton’s natural philosophy (VIII).
II The Science of Man as an attack on Newton’s Foundations
Let us start with Hume’s “Introduction” to the Treatise:
’Tis evident, that all the sciences have a relation, greater or less, to human nature; and that however wide any of them may seem to run from it, they still return back by one passage or another. Even Mathematics, Natural Philosophy, and Natural Religion, are in some measure dependent on the science of Man; since they lie under the cognizance of men, and are judged of by their powers and faculties . . . [W]e ourselves are not only the beings, that reason, but also one of the objects, concerning which we reason
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And as the science of man is the only solid foundation for the other sciences, so the only solid foundation we can give this science itself must be laid on experience and observation (“Introduction,” 4-7).[viii]
I am not the first to note that in this “Introduction” Hume inverts Descartes’ tree of the sciences; the roots are not metaphysics as Descartes thought, but a theory of human nature.[ix] According to Hume “the only solid foundation” for the “science of Man,” in turn the “foundation” for the other sciences, is based “on experience and observation.” Hume’s “science of Man” is not merely a goal in its own right, interesting as that may be,[x] but also requisite to help better understand the other sciences.[xi] Hume also talks of the “changes and improvements we might make in these sciences” (emphasis added). Thus, the “science of man” can instruct the other sciences. Hume’s “science of man” displaces metaphysics as the fundamental form of knowledge of the order of things. How this is supposed to work is left unclear, and maybe this is why in the quote Hume employs the more tentative sounding, “some measure.”
The nature of Hume’s ambitions is even more evident when we put them in context of a text by Newton widely read by Hume’s contemporaries. In the last query of the Opticks, Newton argues:
And if, natural Philosophy in all its Parts, by pursuing this Method, shall at length be perfected, the Bounds of Moral Philosophy will be also enlarged. For so far as we can know by natural Philosophy what is the first Cause, what Power he has over us, and what Benefits we receive from him, so far our Duty towards him, as well as that towards one another, will appear to us by the Light of Nature. (405)
For Newton natural philosophy is, to the degree it provides any knowledge of first causes, a means toward understanding the Deity. This accords well with his views in the “General Scholium” of the Principia: “to treat of God from phenomena is certainly a part of natural philosophy.” (emphasis added) Newton offers a probable, inductive argument (from Design) for God’s existence.[xii] Moreover, Newton sees the perfection of natural philosophy as a kind of foundation of moral philosophy, but does not speak of moral philosophy’s perfection.
Hume’s attack on the argument from design in Section XI of the first Enquiry or the Dialogues is well known. One can see this as Hume correcting Newton and the 18th century Newtonian natural religion advocates on internal, ‘Newtonian’ grounds. While not inaccurate, this underestimates the programmatic ambition of Hume. For in the “Introduction” to the Treatise, Hume claims, first, that the “science of man” is the only solid “foundation” for the other sciences and, second, that moral philosophy (i.e., social science in the broad sense) can, despite some practical difficulties, be as certain as natural philosophy. As Hume says in, “Of the Balance of Trade:” “We need not have recourse to a physical attraction…There is a moral attraction, arising from the interests and passions of men, which is full as potent and infallible” (EMPL, 313; see also the concluding line of the “Dissertation of the Passions:” “It is sufficient for my purpose, if I have made it appear, that, in the production and conduct of the passions, there is a certain regular mechanism, which is susceptible of as accurate a disquisition, as the laws of motion, optics, hydrostatics, or any part of natural philosophy.”)[xiii] Hume’s “Introduction” to the Treatise, then, signals the implicit, epistemological reversal of Newton’s project.
No doubt Hume is in large part motivated to undercut Newtonian attempts to enlist natural philosophy in debates over moral philosophy.[xiv] If Hume can constrain the authority and interpretation of natural philosophy, he cuts off one pillar of support for claims for natural religion. In this strategy -- of constraining the authority of natural philosophy --, Hume finds himself an odd bedfellow with Berkeley, who, in response to Newton’s success, tries to minimize the scope and content of natural philosophy’s authority (e.g., De Motu, 71-2, Principles 66, 106-106).[xv] Of course, Hume intends to replace the priority of metaphysics, preferred by Berkeley, with a “science of man.” In the next section, I analyze further evidence of the epistemic priority of Hume’s “science of man.”
III The Proofs of Common Life
Hume distinguishes between three epistemic categories in descending degree of certainty: “demonstrations;” “proofs,” and “probabilities.” (See especially, Hume’s footnote at the beginning of Section 6 of first Enquiry and Treatise 1.3.11.1.)[xvi] It is a bit confusing that sometimes proofs are presented as a species of probabilities, but in context it is clear when proofs are distinguished from probabilities. Demonstrations are restricted to relations of ideas (first Enquiry, 4.1.1), while proofs and probabilities concern matters of fact. Claims about ‘objects’ immediately present to the senses and memory can be proved. (Cf. footnote to start of Section 6 with 4.1.3-4.) The realm of proof involves common sense claims, e.g., “I see fire burning;” “the apple is green;” “I recall that it rained on Tuesday.” The mitigated skeptic does not doubt these provable facts from common life (see 12.3.25 and also the “wise man” at 10.4). Causal reasoning enables claims that go beyond the immediate evidence of the senses or memory; such claims produce probable belief of varying degrees. (cf. first Enquiry, 4.1.3-4 and 4.2.19) The proofs in the realm of common-life, however, can involve causal claims. This is why Hume can claim that he knows “with certainty” that if a friend threw himself out of the window, “and meet with no obstruction, he will not remain a moment suspended in the air.” (first Enquiry 8.1.20)
Now it’s clear that for Hume at least some experiments in natural philosophy can be part of common life. For example, Hume allows some prism experiments in optics to be a source of very strong “proof.” (Treatise 2.3.9.19; see also “Dissertation of the Passions” p. 140) Such experiments can produce high epistemic confidence. I presume this is the case because the varying experimental effects of the prism, which separates sunlight into different rays, are immediately present to one’s eyes.
Nevertheless, on my reading of Hume’s “mitigated skepticism,” causal claims of metaphysics and even natural philosophy that go beyond common life (e.g., the “origin of worlds”) cannot be “proven.” (first Enquiry, 12.3.25) One might think otherwise[xvii] when it comes to natural philosophy because of two passages. First in “Of Miracles,” Hume asserts that “laws of nature” have been “established” by “firm and unalterable experience.” (first Enquiry, 10.12) Second at Treatise 1.3.11.2, Hume writes that “One would appear ridiculous, who wou’d say, that ‘tis only probable the sun will rise tomorrow, or that all men must dye.” However, I offer alternative readings of both passages.
First there is no evidence that in the passage from “Of Miracles,” Hume has Newtonian or some other natural philosophy in mind. Rather, in context, “laws of nature” refers to the collective experience of mankind going back to pre-history. (This is how Hume also uses “laws of nature” at 4.1.8-9.) For once one understands Newton’s system of the world, it is not easy to overlook how strange Newton’s conception of the universe is.[xviii] Not only do all the most distant particles of the universe attract each other, but attraction between, say, the sun and Jupiter (and all their parts and all other parts of the universe) is mutual (Principia, Book III, Proposition VII, Theorem VII); the acceleration produced by the exercise of a force is simultaneous with that exercise. Leaving aside how and to what extent Hume understood the content of Newton’s Principia, it is implausible to claim that he thought that the collective experience of mankind established Newton’s analysis of the laws of nature.
Moreover, in the passage from the Treatise, Hume is using common-sense language and not the language of natural philosophy in describing orbits of Sun and Earth. Hume appears to be following Berkeley’s Baconian advice -- offered in discussion of the Copernican refutation of the common sense idea that the Sun rises -- that, “we ought to think with the learned and speak with the vulgar.” (Principles, 51) So neither passage ought to support the claim that Hume believes the fundamental claims by natural philosophy about laws of nature are provable.
Hume’s “mitigated skepticism” is not supposed to undermine the reasoning of common life; he puts aside any concerns he has about the ultimate metaphysical status of causes.[xix] Moreover, he insists that “experimental inference and reasoning concerning the actions of others enters so much into human life, that no man, while awake, is ever a moment without employing it.” For example, when, in the context of the rule of law, even “the poorest artificer” brings goods to market and “offers them at a reasonable price,” he can be assured that he will “find purchasers.” (first Enquiry, 8.1.17) As he did with the result of prism experiments, Hume links experimental reasoning with high epistemic confidence. Hume treats causal reasoning in his political economy, even when “abstruse,” (“Of Commerce,” 253) as part of common life. This is why the language of “proof” appears throughout his political economy (see, e.g., “Of Refinement in the Arts,” 276, “Of Balance of Trade,” 311, and “Of Interest,” 297, etc.) In Part I of the Dialogues, even Philo agrees to accept that speculations concerning “trade, or morals, or politics, or criticism” appeal to “common sense and experience” and “remove (at least, in part) the suspicion which we so justly entertain with regard to every reasoning that is very subtile and refined.”