¹ John Locke, Essay concerning Human Understanding, book 3, chap. 5, §5. Henceforth, citations to this work will be given in the text, in abbreviated form (e.g., 3.5.5).

² This is a distinct minority opinion among Locke interpreters. See, e.g., Kendall, Willmoore, John Locke and the Doctrine of Majority Rule (Urbana: University of Illinois Press, 1965), 81–82Google Scholar, 105–13; Miller, Eugene F., “Locke on the Meaning of Political Language: The Teaching of the Essay Concerning Human Understanding,” Political Science Reviewer 9 (Fall, 1979): 178–87Google Scholar; Zinaich, Samuel Jr., John Locke's Moral Revolution: From Natural Law to Moral Relativism (Lanham, MD: University Press of America, 2006)Google Scholar, chap. 3 and conclusion.

³ Peter Laslett's is the classic argument that the Essay and the Second Treatise are incompatible (editor's introduction to Locke, John, Two Treatises of Government, ed. Laslett [Cambridge: Cambridge University Press, 1960], 82–86Google Scholar). For a summary of the overall controversy, see Zinaich, Moral Revolution, chap. 5.

⁴ Versions of this argument are made by Strauss, Leo, Natural Right and History (Chicago: University of Chicago Press, 1953), 212–14Google Scholar, 227–29; Strauss, , “Locke's Doctrine of Natural Law,” in What Is Political Philosophy? and Other Studies (Glencoe, IL: Free Press, 1959), 201–6Google Scholar; Pangle, Thomas, The Spirit of Modern Republicanism: The Moral Vision of the American Founders and the Philosophy of Locke (Chicago: University of Chicago Press, 1988), 136–60Google Scholar, 196–211; Zuckert, Michael P., Natural Rights and the New Republicanism (Princeton: Princeton University Press, 1994), 237–40Google Scholar, 274.

⁵ Arguments for Locke's consistency are made by (among others) Dunn, John, The Political Thought of John Locke: An Historical Account of the Argument of the “Two Treatises of Government” (Cambridge: Cambridge University Press, 1969)CrossRefGoogle Scholar, 92, 198; Grant, Ruth, John Locke's Liberalism (Chicago: University of Chicago Press, 1987)CrossRefGoogle Scholar, 9, 21–25; Rapaczynski, Andrej, Nature and Politics: Liberalism in the Philosophies of Hobbes, Locke, and Rousseau (Ithaca, NY: Cornell University Press, 1987)Google Scholar, 120; Schouls, Peter, Reasoned Freedom: John Locke and the Enlightenment (Ithaca, NY: Cornell University Press, 1992), 183–84Google Scholar, 232.

⁶ “Nominalism” is the name applied to a school of medieval thought that attacked Scholasticism for its theory of forms and formal causes. William of Ockham became its most famous proponent. See, e.g., Ockham, , Quodlibetal Questions Volumes 1 and 2: Quodlibets 1–7, trans. Freddoso, Alfred J. and Kelley, Francis E. (New Haven: Yale University Press, 1991)Google Scholar. I do not make any strong claims about Locke's kinship to Ockham or this school of thought. For overviews of medieval nominalism, see Frederick Copleston, S.J., A History of Philosophy, vol. 3, Late Medieval and Renaissance Philosophy (New York: Doubleday, 1993)Google Scholar, chaps. 3–9; Gillespie, Michael Allen, The Theological Origins of Modernity (Chicago: University of Chicago Press, 2008)CrossRefGoogle Scholar, chap. 1. On Locke's nominalism, see Zinaich, Moral Revolution, 174; Zuckert, Michael, “Locke—Religion—Equality,” Review of Politics 67, no. 3 (2005)CrossRefGoogle Scholar: 420.

⁷ See Locke's passage-by-passage polemic with Edward Stillingfleet, bishop of Worcester, especially the portion related to 2.28 (found in Locke, , An Essay concerning Human Understanding [Amherst, NY: Prometheus Books, 1995], 287–89)Google Scholar. Robert Boyle wrote a number of works rebutting the claim that the new science led to atheism. See especially The Christian Virtuoso: Shewing, That by being addicted to Experimental Philosophy, a Man is rather Assisted, than Indisposed, to be a Good Christian (London: Edward Jones, 1690)Google Scholar, and Some Considerations About the Reconcileableness of Reason and Religion (London: Herringman, 1675)Google Scholar. For modern treatments of this theme, see Marshall, John, John Locke: Resistance, Religion and Responsibility (Cambridge: Cambridge University Press, 1994)CrossRefGoogle Scholar; Shapiro, Barbara J., Probability and Certainty in Seventeenth-Century England: A Study of the Relationships between Natural Science, Religion, History, Law, and Literature (Princeton: Princeton University Press, 1983)Google Scholar; and Wilson, Catherine, Epicureanism at the Origins of Modernity (Oxford: Oxford University Press, 2008)CrossRefGoogle Scholar.

⁸ See Descartes, , Principles of Philosophy, 1.53–61, in The Philosophical Writings of Descartes, trans. Cottingham, John, Stoothoff, Robert, and Murdoch, Dugald, vol. 1 (Cambridge: Cambridge University Press, 1985)Google Scholar, 177–291; Arnauld, Antoine and Nicole, Pierre, Logic or the Art of Thinking (= the Port-Royal Logic), ed. Buroker, Jill Vance (Cambridge: Cambridge University Press, 1996)CrossRefGoogle Scholar, 30–32, 37, 41.

⁹ Robert Boyle, Considerations and Experiments concerning the Origin of Forms and Qualities, in The Works of the Honourable Robert Boyle, Esq., epitomized by Richard Boulton (London, 1699), 3, 4, 17 (available in facsimile through the website Early English Books Online). Henceforth this work will be cited in the text and abbreviated as FQ.

¹⁰ See FQ, 7, 12, 22–26, 34, 43; Alexander, Peter, Ideas, Qualities and Corpuscles: Locke and Boyle on the External World (Cambridge: Cambridge University Press, 1985)Google Scholar, chaps. 2 and 3.

¹¹ See Aristotle, Metaphysics 3.4, Physics 1.7, 1.9, 2.3; Aristotle's Physics: A Guided Study, ed. Sachs, Joe (New Brunswick, NJ: Rutgers University Press, 1995)Google Scholar, 254; Witt, Charlotte, Substance and Essence in Aristotle: An Interpretation of Metaphysics VII–IX (Ithaca: Cornell University Press, 1989)Google Scholar, 66.

¹² Alexander, Ideas, Qualities and Corpuscles, 40–43, 52; Boas, Marie, Robert Boyle and Seventeenth-Century Chemistry (Cambridge: Cambridge University Press, 1958)Google Scholar, 77. See also FQ, book 1, chaps. 1 and 4.

¹³ Boyle, Robert, A Free Enquiry into the Vulgarly Received Notion of Nature, ed. Davis, Edward B. and Hunter, Michael (Cambridge: Cambridge University Press, 1996)CrossRefGoogle Scholar.

¹⁴ See the Stillingfleet broadsides, referred to in note 7 above. See also Cranston, Maurice, John Locke: A Biography (New York: Longmans, Green, 1957)Google Scholar, 276, 410; Parker, Kim Ian, The Biblical Politics of John Locke (Waterloo, ON: Wilfred Laurier University Press, 2004)Google Scholar, 33; Zinaich, Moral Revolution, 80; Zuckert, Natural Rights and the New Republicanism, xvi. Near the end of Locke's life, the Essay was suppressed at Oxford (Marshall, Resistance, Religion and Responsibility, 452; Cranston, John Locke, 429).

¹⁵ The domain of “mode” is also somewhat different for Locke, inasmuch as attributes such as color he places in the category of “secondary qualities” rather than modes, and does not apply “modes” to the form of whole objects (which constitute a separate category of “complex idea”). See Essay, 2.8, 2.12.

¹⁶ Aristotle, Posterior Analytics 1.33; Metaphysics 3.4. See also Plato, Republic 476d–480a, 533b–534a; Hacking, Ian, The Emergence of Probability: A Philosophical Study of Early Ideas about Probability, Induction, and Statistical Inference (Cambridge: Cambridge University Press, 2006)CrossRefGoogle Scholar, chap. 3.

¹⁷ It is not clear exactly how this is to take place in Aristotle's view, though he outlines a possible process at the conclusion of the Posterior Analytics (2.19). For some of the difficulties in this account, see Barnes's commentary on the relevant section in Aristotle's Posterior Analytics, trans. with notes by Barnes, Jonathan (Oxford: Oxford University Press, 1975), 248–60Google Scholar. My account of Aristotle ignores some of the problems and subtleties of Aristotle's argument, not to mention the possibility that Aristotle was not fully serious about his “doctrine” of forms (see Bolotin, David, An Approach to Aristotle's Physics, With Particular Attention to the Role of His Manner of Writing [Albany: SUNY Press, 1998])Google Scholar. Most such subtleties were lost on the Scholastics, though, and it is “Scholastic Aristotelianism” with which Locke is contending.

¹⁸ Aristotle, De anima 3.4. Aquinas and the Scholastics called this the “agent intellect”; Summa 1.79.1–5. See also Yolton, John, introduction to Perceptual Acquaintance from Descartes to Reid (Minneapolis: University of Minnesota Press, 1984)Google Scholar.

¹⁹ See Ross, David, Aristotle (London: Methuen, 1971)Google Scholar, 71; Witt, Substance and Essence, 100; Aquinas, Summa 1.48–49, 55.2, 79–119. See also Locke, Essay, 4.8.

²⁰ Pufendorf, Samuel, De Jure Naturae et Gentium Libri Octo (hereafter JNG), trans. Oldfather, C. H. and Oldfather, W. A., vol. 3 (Washington, DC: Carnegie Endowment for International Peace, 1934)Google Scholar; Pufendorf, , On the Duty of Man and Citizen, trans Silverthorne, Michael, ed. Tully, James (Cambridge: Cambridge University Press, 1991)Google Scholar.

²¹ Some Thoughts concerning Education, in On Politics and Education, ed. Penniman, Howard R. (Roslyn, NY: Walter J. Black, 1947), 203–388Google Scholar; Some Thoughts concerning Reading and Study for a Gentleman, in The Works of John Locke (1794; repr., London: Routledge/Thoemmes, 1997)Google Scholar, 2:408. It seems, but is not entirely clear, that Locke is here placing his own and Pufendorf's works in the same “kind,” that is, works on “the original of societies, and the rise and extent of political power.” Pufendorf's thoughts on those subjects are not fully compatible with those of Locke. Locke also recommends Pufendorf for educational purposes in a letter to Richard King, 25 August 1703, very shortly before his death in 1704 (The Works of John Locke in Nine Volumes, 12th ed. [London: Rivington, 1824], 9:305–9Google Scholar). On the links between Locke and Pufendorf, see also Tully, James, A Discourse on Property: John Locke and His Adversaries (Cambridge: Cambridge University Press, 1980), 5–8CrossRefGoogle Scholar; Buckle, Stephen, Natural Law and the Theory of Property: Grotius to Hume (Oxford: Oxford University Press, 1991)Google Scholar, chaps. 2 and 3.

²² JNG, 1.1.3. “Accident” in the Scholastic lexicon was a trait not “essential” to an object. Modus is the word in Pufendorf's Latin text. On Pufendorf's pioneering use of “mode,” see also Schneewind, J. B., “Pufendorf's Place in the History of Ethics,” Synthese 72, no. 1 (1987): 124–30CrossRefGoogle Scholar; Tully, Discourse on Property, 9–10.

²³ JNG, 1.1.16; 1.2.3; 2.2.3; see also Grotius, Hugo, De Jure Belli ac Pacis (hereafter JBP), in The Law of War and Peace, trans. Kelsey, Francis W. (New York: Carnegie Endowment for International Peace, 1925)Google Scholar, 1.1.10.4, 2.2.2.1.

²⁴ 1.2.4. Pufendorf cites De Homine, chap. 10, where Hobbes argues that before civil law there is no justice. Hobbes acknowledges in Leviathan that the natural laws are laws properly speaking only if attributed to God (chap. 15, end; see also chaps. 21, 26, 31).

²⁵ JNG, 2.3. Pufendorf also makes this argument in his early (1660) work Elementorum Jurisprudentiae Universalis, in The Elements of Universal Jurisprudence, trans. Oldfather, W. A., vol. 2 (Washington, DC: Carnegie Endowment for International Peace, 1931)Google Scholar, definition 13.14. Here, Pufendorf already lays out his notion of a demonstrative moral science, though without the theory of moral modes.

²⁶ Original sin entails that the (tainted) nature we have is not the pristine nature God gave us. Inferring natural law, empirically, from human nature as we find it would under these conditions be problematic (though certainly not impossible: this was the endeavor of Christian natural law thinking from at least the time of Aquinas [Summa 1.80; 1.82; 2.1.91.6; 2.1.94]).

²⁷ For other accounts of Locke's debt to Pufendorf, see Tully, Discourse on Property, 9, 23; Buckle, Natural Law, chaps 2, 3; Zuckert, Natural Rights and the New Republicanism, chaps. 7, 9.

²⁸ See, for example, Ayers, Michael, Locke: Epistemology and Ontology (New York: Routledge, 1991)Google Scholar, 2:131, 189, 197; Kim Ian Parker, The Biblical Politics of John Locke, 126; A. Simmons, John, The Lockean Theory of Rights (Princeton: Princeton University Press, 1992), 32–34Google Scholar, 45.

²⁹ First Treatise, §88. Even the right of property, I have argued, rests ultimately on a divine mandate geared toward the good of mankind as a whole. See Forde, Steven, “The Charitable John Locke,” Review of Politics 71, no. 3 (2009): 432–35CrossRefGoogle Scholar, 448–49. See also Grant, Locke's Liberalism, 36–42; Sigmund, Paul E., “Jeremy Waldron and the Religious Turn in Locke Scholarship,” Review of Politics 67, no. 3 (2005)CrossRefGoogle Scholar: 414. Ayers correctly points out that Locke's procedure (as I have argued with respect to Pufendorf) presumes a consistent and nonarbitrary divine will (Locke: Epistemology and Ontology, 2:189). This interpretation might also lessen the gap that is usually found between Locke's mature works and his early Questions concerning the Law of Nature, trans. Horwitz, Robert, Clay, Jenny Strauss, and Clay, Diskin (Ithaca, NY: Cornell University Press, 1990)Google Scholar. Locke there argues naturalistically (e.g., 101, 227). As we have just seen, though, this does not necessarily make him philosophic kin to Grotius or Thomas. On this issue, see Ashcraft, Richard, Revolutionary Politics and Locke's “Two Treatises of Government” (Princeton: Princeton University Press, 1986)Google Scholar, 75, 258; Ayers, Locke: Epistemology and Ontology, 2:189; Zinaich, Moral Revolution, chap. 4; Zuckert, Natural Rights and the New Republicanism, chap. 7.

³⁰ See Grotius, JBP, Prolegomena 11; 1.1.10.1; 1.1.10.5; 1.2.5.1; Cicero, De Officiis 1.4; Hooker, Richard, Of the Laws of Ecclesiastical Polity, in The Folger Library Edition of the Works of Richard Hooker, ed. Hill, W. Speed (Cambridge, MA: Belknap Press of Harvard University Press, 1977)Google Scholar, 1.3, 8. Francisco Suárez summarizes the rationalist and voluntarist schools of Christian thought in his 1612 work On Laws and God the Lawgiver, in Selections from Three Works, trans. Williams, Gwladys L. et al. , vol. 2 (Oxford: Oxford University Press, 1944)Google Scholar, 2.6.3. See also Forde, Steven, “Natural Law, Theology, and Morality in Locke,” American Journal of Political Science 45, no. 2 (2001): 398–400CrossRefGoogle Scholar; Simmons, Theory of Rights, 103.

³¹ Cudworth, Ralph, The True Intellectual System of the Universe (London: Richard Royston, 1678; repr., London: Garland, 1978), 147–71Google Scholar. See also Culverwell, Nathaniel, An Elegant and Learned Discourse of the Light of Nature, ed. Greene, Robert A. and McCallum, Hugh (Indianapolis, IN: Liberty Fund, 2001)Google Scholar, chaps. 3, 5, 6; Whichcote, Benjamin, “The Use of Reason in Matters of Religion,” in The Cambridge Platonists, ed. Patrides, C. A. (Cambridge, MA: Harvard University Press, 1970), 42–47Google Scholar. Among commentators, see Patrides, editor's introduction to Cambridge Platonists, 10, 26, 30; Shapiro, Probability and Certainty, 88–89; Schneewind, “Pufendorf's Place,” 130, 148; Tully, Discourse on Property, xvii–xix; Wojcik, Limits of Reason, 126–29.

³² Essay, 1.3.6, 12; see also 1.3.5; 2.27.26; 2.28.4–5, 15; 3.11.16; Some Thoughts concerning Education, §§61, 135–36, 139.

³³ Locke's friends William Molyneux and James Tyrell tirelessly if gently prodded him to write the ethical treatise toward which the Essay points. Locke's reply to Molyneux is seen in his letters to him of 20 September 1692, 19 January 1694, and 30 March 1696, in Works, 8:292–95, 330–33, 375–78. His exchanges with Tyrell may be found in The Correspondence of John Locke, ed. de Beer, E. S., vol. 4 (Oxford: Oxford University Press, 1979), 101, 110–13Google Scholar. Locke's short essay “Of Ethic in General” (in Goldie, Mark, Locke: Political Essays [Cambridge: Cambridge University Press, 1997], 297–304Google Scholar) is supposed to have been intended as a moral demonstration and concluding chapter to the Essay. It was never completed, and in its current state it adds nothing to the Essay regarding these questions.

³⁴ 2.11.10. Jeremy Waldron plausibly identifies “abstraction” as the critical trait (God, Locke, and Equality: Christian Foundations of John Locke's Political Thought [Cambridge: Cambridge University Press, 2002], 75–80Google Scholar).

³⁵ For other discussions of this issue, see Ayers, Locke: Epistemology and Ontology, 2.188–89; Myers, Peter C., Our Only Star and Compass: Locke and the Struggle for Political Rationality (New York: Rowman and Littlefield, 1998)Google Scholar, 56, 67.

³⁶ Locke says that our own existence is the one empirical fact of which we can be certain (4.3.21).

³⁷ 4.10.1, 9; 4.3.6, 21; 4.9; 4.11.13; 4.13.3. Ayers discusses this proof at greater length (Locke: Epistemology and Ontology, chap. 14).

³⁸ For Locke's admission that he never provided an adequate proof, see his letter to William Molyneux of 19 January 1694, in Correspondence, 4:784–87 (see also 767–68). He tended to be evasive when asked why he did not complete this part of his natural theology. On the thorny problem of Locke's theological-moral proof, see Zuckert, “Locke—Religion—Equality,” 423.

³⁹ 2.21.70; 4.11.12. Locke does at one point claim that from the existence of “an eternal, most powerful, and most knowing Being” we can deduce all the other attributes we “ought” to attribute to him (4.10.6). In his polemic with the bishop of Worcester over the Essay (see above, note 7), Locke wrote (in the context of a discussion of Cicero and classical philosophy), “though the light of nature gave some obscure glimmering of a future state, yet human reason could attain to no clearness or certainty about it” (Essay, 479).

⁴⁰ This is somewhat different from the interpretation of Myers (Star and Compass, 25, 54–55, 179), who finds that Locke's moral demonstration lacks certainty in principle.

⁴¹ See the citations in note 33, above.

⁴² See Yolton, John W., Locke and the Compass of Human Understanding: A Selective Commentary on the “Essay” (Cambridge: Cambridge University Press, 1970)Google Scholar, 172; Coby, Patrick, “The Law of Nature in Locke's Second Treatise: Is Locke a Hobbesian?,” Review of Politics 49, no. 1 (1987): 3–28CrossRefGoogle Scholar; Rabieh, Michael S., “The Reasonableness of Locke, or the Questionableness of Christianity,” Journal of Politics 53, no. 4 (1991)CrossRefGoogle Scholar: 941; Hobbes, Leviathan, chaps. 14–15; see also Second Treatise, §12.

⁴³ There is debate as to whether it is misleading to call Locke a “hedonist.” See, e.g., Aarsleff, Hans, “The State of Nature and the Nature of Man in Locke,” in John Locke: Problems and Perspectives, ed. Yolton, John W. (Cambridge: Cambridge University Press, 1969)Google Scholar, 127; Grant, Locke's Liberalism, 44; Marshall, John Locke, 188, 194, 315; Tarcov, Nathan, Locke's Education for Liberty (Chicago: University of Chicago Press, 1984)Google Scholar, 5, 77. I believe that Locke's reliance on happiness and pleasure make the label appropriate, indeed unavoidable. On the ambiguous role of corporeality in Locke's philosophy, see Waldron, God, Locke, and Equality, 67, 70, 111.

⁴⁴ Kant's clearest statement of these principles is in the Foundations of the Metaphysics of Morals. On the parallel between Locke and Kant, see also Rapaczynski, Nature and Politics, 161.

⁴⁵ See Abbott, Thomas Kingsmill, “Memoir of Kant,” in Kant's Critique of Practical Reason and Other Works on the Theory of Ethics, trans. Abbot (London: Longmans, Green, 1889)Google Scholar.

⁴⁶ We may think once again of Locke's example of drunkenness, which gains moral significance only by imposition of a moral mixed mode (Essay, 2.28.15). See Pufendorf, JNG, 1.1.4; Hume, David, A Treatise of Human Nature: Being an Attempt to introduce the experimental Method of Reasoning into Moral Subjects, ed. Selby-Bigge, L. A. (Oxford: Oxford University Press, 1965)Google Scholar, 3.1.1.