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Published online by Cambridge University Press: 05 May 2010
Recent interpretations of Locke's primary/secondary quality distinction have tended to emphasize Locke's relationship to the corpuscularian science of his time, especially to that of Boyle. Although this trend may have corrected the unfortunate tendency to view Locke in isolation from his scientific contemporaries, it nevertheless has resulted in some over- simplifications and distortions of Locke's general enterprise. As everyone now agrees, Locke was attempting to provide a philosophical foundation for English corpuscularianism and one must therefore look not only at the current scientific hypotheses but also at the nature of the philosophical foundation Locke was attempting to erect. In particular, Locke made an attempt, based on epistemological principles, to give a philosophical justification of atomistic corpuscularianism. Moreover, he was not content to give this justification post hoc—the epistemological foundation was prior to, and determined the framework for, the details of the correct scientific theory. Locke's epistemology made legitimate an atomistic theory, one making crucial use of the notion of solidity in the definition of the elementary particles, although it did not prejudge the details of this theory.
1 See, among others, chaps. I and 2 of Mandelbaum's, MauricePhilosophy, Science and Sense Perception (Baltimore, MD: Johns Hopkins University Press, 1964)Google ScholarCurley, E. M., “Locke. Boyle and the Distinction Between Primary and Secondary Qualities”, Philosophical Review 81 (October 1972), 438–464CrossRefGoogle Scholar and Alexander, P.. “Boyle and Locke on Primary and Secondary Qualities”, Ratio 16 (1974), 51–67Google Scholar.
2 Descartes, Principles of Philosophy, Part II, IV and XX, in Haldane, E. S., Ross, G. R. T., eds., The Philosophical Works of Descartes, vol. I (London: Cambridge University Press, 1972), 255 and 264Google Scholar.
3 Ibid., Part II, LX1V.
4 Ibid., Part IV, CCII.
5 Many of Descartes' claims lead to this ultimate conclusion. See, among many other places, Principles, Part II, LXIV and CCIII; and the discussion of the piece of wax in the second Meditation.
6 It might be objected, even at this point, that the kind of solidity that Locke thinks is essential to body is not, forexample, hardness but impenetrability, that impenetrability has nothing especially to do with atomism, and that Locke's position, correctly interpreted, is not really different from Descartes'. However, we understand by solidity precisely what Locke says at the beginning of Essay, 11,4,1: “The Idea of Solidity we receive by our Touch; and it arises from the resistance which we find in Body, to the entrance of any other Body into the Place it possesses, till it has left it….” At the end of this passage, Locke explicitly says that he distinguishes solidity from impenetrability “which is negative, and is, perhaps, more a consequence of solidity, than solidity itself. We believe that this passage shows that solidity is a qualitative notion, one that is not admissible as a primary quality on the Cartesian geometrical view of primary qualities. Moreover, on our interpretation, the indivisibility of corpuscles is not primarily what is at issue in the debate between Descartes and Locke over atomism. See also footnote 29. For more discussion of these points, see Norbert Hornstein, “Skepticism and Nativism: Descartes and Locke on Innate Ideas”, forthcoming in a Festschrift for Richard POpkin.
7 We do not mean to imply that Locke was directly influenced by Newton or vice versa, since the third rule of philosophy did not appear until after the Essay was written. However, even though we shall put no weight upon it, Locke was not unfamiliar with Newton's work or Newton with Locke's. See Axtell, James, “Locke, Newton and the Two Cultures”, in John Locke: Problems and Perspectives, ed. Yolton, John (London: Cambridge University Press, 1965),Google Scholar and Rodgers, G. A. J., “Locke's Essay and Newton's Prineipia”, Journal of the History of Ideas 39 (1978), 217–232.CrossRefGoogle Scholar In addition, it is interesting to note that a copy of the Prineipia given to Locke by Newton in the early 1690s contains a marginal notation introducing what was to become the third rule of philosophy (see Cohen, I. Bernard, An Introduction to Newton's Prineipia [Cambridge, MA: Harvard University Press. 1971], 24).CrossRefGoogle Scholar Our claim is simply that Locke and Newton were concerned with philosophical problems that were not of primary concern to Boyle. See Mandelbaum, , Philosophy, chap. 2, especially 87–88Google Scholar.
8 For relevant discussions of Newton see McGuire, J. E., “Atoms and the ‘Analogy of Nature’: Newton's Third Rule of Philosophizing”, in Studies in the History and Philosophy of Science I (1970), 3–58CrossRefGoogle ScholarMcGuire, J. E., “The Origin of Newton's Doctrine of Essential Qualities”. Centannis 12 (1968). 233–260Google Scholar and Koyre, A., Newtonian Studies (Chicago: University of Chicago Press, 1965), chap. 6CrossRefGoogle Scholar.
9 Mandelbaum, Philosophy, chap. 2.
10 The Boy lean reading of Locke argues that Locke believes that primary qualities are those which are required by corpuscular explanations. For example, as Mandelbaum argues in an influential essay, “the basis on which Locke established his theory of the primary qualities was his atomism…. Thus, instead of viewing Locke's doctrine of the primary and secondary qualities as a doctrine which rests on an analysis of differences among our ideas, his doctrine is to be understood as a theory of physical entities, and of the manner in which our ideas are caused. To this extent the Berkeleian criticism of Locke's distinction between primary and secondary qualities is wholly beside the point, for it rests on an assumption which Locke did not share—that all distinctions concerning the nature of objects must be based upon, and verified by, distinctions discernible within the immediate contents of consciousness” (27-28). This Boylean reading is seconded by Curley who argues that for Locke our ideas of primary qualities of bodies are resemblances of them and our ideas of secondary qualities are not, in the sense that our causal accounts will make essential reference to primary qualities, whereas they will not make essential reference to secondary qualities. Thus, only primary qualities are involved in our causal explanations. As Curley says, in the context of discussing questions of perception, “Locke's characterization of the primary qualities as 'original' qualities of objects rightly suggests what we would now put by saying that they are qualities designated by the primitive terms in the scientific theory of perception” (454). This reading of Locke cites the numerous instances in the Essay where Locke gives corpuscularian explanations and tries to make the epistemological distinction between primary and secondary qualities dependent on the nature of these explanations. Thus, the argument from scientific explanation is thought to be Locke's major argument in making out an adequate distinction between primary and secondary qualities.
11 All references to the Essay Concerning Human Understanding will be to the Nidditch edition (Oxford: Oxford University Press, 1975)Google Scholar.
12 Descartes wished to explain all natural phenomena by reference to geometrical properties (and, of course, motion), and these properties were for Descartes what we would now call primary qualities. See footnote 2 above.
13 Although Descartes is sometimes called a corpuscularian, he makes solidity (hardness) a derivative notion. See Principles, Part II, IV, and Part II, XX. What is important for our discussion is that Descartes was clearly not an atomist in the way that Locke unambiguously was.
14 See especially Curley, “Locke, Boyle”.
15 See also Locke's Essay, 11, 21, 73.
16 Quoted in Mandelbaum, , Philosophy, 82–83Google Scholar.
17 Cited in McGuire, , “Origin of Newton's Doctrine”, 237Google Scholar.
18 Cited in McGuire, , “Atoms and the 'Analogy of Nature'”, 226Google Scholar.
19 See Mandelbaum, Philosophy, chap. 2.
20 This is discussed by McGuire in “Origin of Newton's Doctrine”.
21 See Koyre, , Newtonian Studies, 272Google Scholar.
22 On Gassendi, see Koyre, A., Metaphysics and Measurement (Cambridge. MA: Harvard University Press, 1968),Google Scholar chap. 5. For a more recent discussion of Gassendi, see Bloch, O., La Philosophic de Gussendi (The Hague, Netherlands: Martinus Nijhoff. 1971)Google Scholar.
23 All page references to Berkeley, unless otherwise stated, are from Turbayne, Colin Murray, ed.. Principles, Dialogues, and Correspondence, Library of Liberal Arts Series (Indianapolis, IN: Bobbs-Merrill, 1965)Google Scholar.
24 There is some controversy as to whether Berkeley's arguments were meant to apply ' mainly to Locke. However, for our purposes it is enough that the kind of arguments that Berkeley uses did apply to Locke. For some interesting discussion see Popkin, Richard, 'Berkeley and Pyrrhonism”, The Review of Metaphysics 5 (1951–1952), 223–246,Google Scholar and Bracken, Harry, “Boyle, Berkeley, and Hume”, Eighteenth Century Studies ll (1977-1978), 227–245CrossRefGoogle Scholar.
25 See Philosophical Commentaries #657a, reprinted in Armstrong, D., ed., Berkeley's Philosophical Writings (New York: Collier, 1965)Google Scholar.
26 Locke, Essay, 11, 1,2, and Berkeley, Principles, I.
27 Margaret Wilson has cogently argued this point in an unpublished paper, “Locke and Mind Body Dualism”, given to the Harvard Philosophy Club, April 1978. For a discussion of related issues see her “Superadded Properties: The Limits of Mechanism in Locke, ;, American Philosophical Quarterly 16 (April 1979). 143–150Google Scholar.
28 It might also be argued that Locke believed that we mean by “body” “something that is solid”. Locke does seem to argue this way in 11,13,11 where he is obviously opposing himself to Descartes. He claims here that we do not mean by “body” just “extension” but also include in our meaning of “body” the notion of solidity. One might think, based on this passage, that Locke could argue that primary qualities are included in our very meaning of “body”, while secondary qualities are not. But given Locke's views on the relation between the meaning of our words and our ideas, it is unlikely that this reading of him would save him from the difficulties we have already detailed. Moreover, when Locke goes to flesh out his claim that by “body” we mean “something that is solid” he writes, “Solidity is so inseparable an Idea from Body that upon that depends its filling of Space, its Contact, Impulse, and Communication of Motion upon Impulse” (11,13,11). That is, the quality of solidity is necessary to the corpuscularian hypothesis. But, as we have argued, it is this hypothesis which Locke is attempting to ground epistemologically. He does not just argue that solidity is a primary quality because it is needed for the truth of the corpuscularian hypothesis. In addition, it would make Locke's views rather uninteresting to contend that his major arguments on this point depended merely on the meaning of our words. Finally, our ordinary conception of body and the meaning we attach to this word on the basis of this conception is more in accord with Aristotelian common sense than it is with corpuscularian physics. As many practitioners of seventeenth-century physics recognized, their physics had to undermine common sense and our ordinary conceptions, if it was to be successful. On this point see A. Koyre, Metaphysics and Measurement, chap. 1, and the references he makes therein to the articles by Tannery and Duhem.
29 Although Berkeley refers to hardness and not to solidity, solidity, hardness, impenetrability, and resistance were often interchanged. See, for example, our quotation above from Newton's third rule for reasoning in philosophy. The relationship between all of these concepts is unclear throughout most of the discussion that we have cited.
30 In the Dialogues, Berkeley appears to use the variability argumentto draw the stronger conclusion that not only do we not know what the true primary qualities of an object are but that primary qualities are not really in objects at all. However, Berkeley's specific conclusions are irrelevant to our argument.
31 See both Curley, “Locke, Boyle”, and Alexander, “Boyle and Locke”.
32 See Mandelbaum, Philosophy, 85.
33 Koyre, Metaphysics and Measurement, chap. 1.
34 See our quotation from Newton's third rule above.
35 See, for example, Hume's criticisms which lead to the conclusion that the “modern philosophy … leaves us no just or satisfactory idea of solidity, nor consequently of matter” (Hume, A) Treatise of Human Nature, Book l.Part 4, chap. 4 [Oxford: Oxford University Press, 1888])Google Scholar.
36 If primary qualities in general are dependent on abstract ideas and if, as Locke says, abstract ideas are “Creatures of our own making” (11,3,11), then to ascribe these general qualities to objects would be to ascribe fictions to them. Berkeley's arguments are based on his emphasizing that since only ideas of particulars are based in sensation, an empiricist epistemology has difficulty epistemologically grounding ideas of general qualities. There are also some important differences between Berkeley's and Locke's theories of abstract ideas that are relevant to this discussion, but we shall discuss these in a forthcoming paper.
