¹ AT III.266; CSMK:163. Descartes, René, The Philosophical Writings of Descartes (trans. Cottingham, John, Stoothoff, Robert, Murdoch, Dugald. Volumes I and II (Cambridge University Press)Google Scholar; The Philosophical Writings of Descartes: The Correspondence (trans. John Cottingham, Robert Stoothoff, Dugald Murdoch, Anthony Kenny. Volume III (Cambridge University Press, 1985, 1984, 1991)).

² On Descartes’ dualism see my ‘Descartes’ Dualism: Correcting some Misconceptions’, Journal of the History of Philosophy 39.2 (2001), 215–238, and my Self, Reason and Freedom: A New Light on Descartes’ Metaphysics (Routledge 2013/2016).

³ Hume, David, Treatise of Human Nature (Selby-Bigge, L.A. (ed.) 2nd ed. Revised by Nidditch, P.H.. Oxford: Clarendon Press, 1978), I.iv.iiGoogle Scholar.

⁴ Rule Three AT X.369.

⁵ AT VII.161 Definition VI.

⁶ Letter to Mersenne 21 April 1641 AT III.362; CSMK:180.

⁷ Peri Psyches, Book III. See my ‘Self and Self-Consciousness: Aristotelian Ontology and Cartesian Duality’, Philosophical Investigations 32.2 (2009), 134–62. Aristotle exempts nous from hylomorphism.

⁸ Synopsis AT VII.14; AT VII.80 passim. Letter to Regius December 1641 AT III.461; CSMK:200.

⁹ Principles II.21–22.

¹⁰ AT VII.78. I'm not suggesting that mind is really distinct only from body, but not the body; I'm simply emphasising the distinction between the latter two. See fn.36; sec.6 below; my op.cit., note 2.

¹¹ Third Meditation. Letter to Gibieuf 19 January 1642 AT III.474–8; CSMK: 201–203.

¹² Some deny that Descartes is a monist regarding corporeal substance, arguing that he's a pluralist. For a brief survey see Kaufman, Dan ‘Cartesian Substances, Individual Bodies, and Corruptibility’, Res Philosophica (2014), 71–103CrossRefGoogle Scholar; he defends pluralism. This cannot be discussed here, but there seems to be a conflation between ‘corporeal substance’ strictly speaking, and Descartes’ use of ‘res sive substantia’ to refer to bodies.

¹³ AT VII.86; AT VII.28.

¹⁴ Principles II.25.

¹⁵ AT VII.86.

¹⁶ For example, R.C. Richardson, ‘The “Scandal” of Cartesian Interactionism’, Mind 91 (1982), 20–37, doesn't discuss Descartes’ Causal Principle; this may explain Richardson's concerns, despite arguing that heterogeneity doesn't render mind–body interaction incoherent.

¹⁷ Radner, Daisie, ‘Is There a Problem of Cartesian Interaction?’, Journal of the History of Philosophy 23 (1985), 35–49CrossRefGoogle Scholar: 41–42, claims there are three different causal principles (see below), and whom Cottingham, John, Descartes (Oxford: OUP 1986), 49–54Google Scholar and 138, seems to follow, though combining her first two into what he calls the ‘Causal Adequacy Principle’.

¹⁸ AT VII.40.

¹⁹ AT VII.40–41.

²⁰ ‘The concept of an efficient cause [does not] require that it be prior in time to its effects. On the contrary, the concept of a cause is, strictly speaking, applicable only for as long as the cause is producing its effect, and so it is not [temporally] prior to it.’ (First Set of Replies AT VII.108).

²¹ The distinction between a priori and a posteriori in Descartes is not the same as our distinction between reason and experience; the latter is what I use here. For Descartes, reasoning a priori is reasoning ‘from prior/former’, from causes or principles; reasoning a posteriori is reasoning ‘from posterior/latter’, from effects. (The World AT XI.47).

²² Gibb, Sophie, ‘Defending Dualism’, Proceedings of the Aristotelian Society 115 (2015), 131–146CrossRefGoogle Scholar: 140.

²³ Martin, C.B., The Mind in Nature (Oxford: OUP, 2008)Google Scholar, secs.5.3 and 7.4.

²⁴ By ‘formal cause’ Descartes doesn't mean what the late Scholastics meant, in terms of which the substantial form of an entity was the emanative cause of its properties. Descartes rejects both substantial forms and emanations.

²⁵ AT VII.242.

²⁶ AT VII.236–7.

²⁷ AT V.156–158; AT VII.57.

²⁸ O'Neill, Eileen, ‘Mind–Body Interaction and Metaphysical Consistency: A Defence of Descartes’, Journal of the History of Philosophy 25.2 (1987), 227–45CrossRefGoogle Scholar.

²⁹ O'Neill, op,cit. note 28: 243. Also Loeb, Louis E., From Descartes to Hume (Ithaca: Cornell University Press, 1981), 155–6Google Scholar.

³⁰ Letter to Mersenne October 1640 AT III.211–212. Descartes (AT III.694; CSMK:228); I owe it also to Peter J. King; see sec.9 below.

³¹ Fourth Set of Replies AT VII.236.

³² AT IXA.213.

³³ Kenny, Anthony, Descartes: A Study of his Philosophy (New York: Random House, 1968) 222–3Google Scholar. Wilson, Margaret, Descartes: Ego Cogito, Ergo Sum (London: Routledge & Kegan Paul, 1978), xxix–xxxGoogle Scholar. Williams, Bernard, Descartes: The Project of Pure Enquiry (Sussex: Harvester Press, 1978), 278–9Google Scholar. Cottingham, op. cit. note 17: 48–55, 137–141.

³⁴ Daniel Garber, ‘Descartes’ Occasionalism’ (in Nadler (ed.) 1993; op.cit. note 36) 9–26: 20–1.

³⁵ Hatfield, Gary, ‘Force (God) in Descartes’ Physics’, Studies in History and Philosophy of Science 10 (1979): 113–40CrossRefGoogle Scholar: 134–5.

³⁶ Nadler, Steven (ed.), Causation and Explanation in Early Modern Philosophy (Pennsylvania: Pennsylvania State Press, 1993)Google Scholar, ‘Introduction’, 3–4.

³⁷ Flage, D.E. and Bonnen, C.A., ‘Descartes on Causation’, The Review of Metaphysics 50 (1997), 841–72Google Scholar: 842 and 868.

³⁸ AT VII.30.

³⁹ The World AT XI.7; Principles IV.198.

⁴⁰ Letter to Regius, January 1642 AT III.500; CSMK:207.

⁴¹ Fifth Set of Replies AT VII.351.

⁴² ‘Perfections’ (plural) can mean attributes, though not properties: ‘all the perfections which I attribute to God’ (AT VII.49), or ‘these perfections are merely attributes of a substance’. (AT VII.168) The more perfections something has, the more reality or perfection it has.

⁴³ AT VII.165.

⁴⁴ AT VII.116.

⁴⁵ Letter to Clerselier 23 April 1649; AT V.356; CSMK:377; to Mersenne 16 October 1639 AT II.598; CSMK:139.

⁴⁶ Principles II.37 and 43; Principles I.37–44.

⁴⁷ Physicalism equates ‘natural’ with ‘physical’, but while everything physical might be natural, the converse isn't true. Descartes’ ‘natural light of reason’ refers neither to physical nor to supernatural or divine illumination. Physicalism also equates ‘objective’ with ‘physical’, but while everything physical might be objective, what's objective encompasses more than the physical. (Principles III.4).

⁴⁸ Definition X AT VII.162.

⁴⁹ Discourse V AT VI.59.

⁵⁰ AT VII.78.

⁵¹ Descartes’ response to the objection that he said ‘not one word about the immortality of the human mind’ (AT VII.127), is: ‘from the fact that the soul is distinct from the body [it doesn't follow] that it is immortal’. It's possible ‘that its duration comes to an end simultaneously with the end of the body's life’. (Second Set of Replies AT VII.153).

⁵² Sixth Meditation AT VII.78; the vice versa is essential because without it no real distinction is, or can be, drawn.

⁵³ Third Meditation AT VII.45.

⁵⁴ First Set of Replies AT VII.108–9.

⁵⁵ Axiom VI AT VII.165.

⁵⁶ I.P7 Proof n.2. de Spinoza, Benedict, Spinoza: The Complete Works (Shirley, Samuel (trans.), Morgan, Michael I. (ed.) Indianapolis: Hackett Publishing Company, 2002)Google Scholar.

⁵⁷ As the literature is well known, there's no need to list everyone who misconstrues ‘reality or perfection’ as properties and attributes to Descartes up to three causal principles, a containment principle (O'Neill, op. cit. note 28: 230), a pre-existence principle, and an at least-as-much principle (Radner, op.cit., note 17). For a brief survey, see Schmaltz, Tad, ‘Deflating Descartes's Causal Axiom’ (Early Modern Philosophy: Oxford Studies volume III. Garber, Daniel and Nadler, Steven (eds) Oxford: OUP, 2006), 1–31Google Scholar; Schmaltz falls in that category; see also his ‘Containment, Eminently vs. Formally’ ((regrettably in) The Cambridge Descartes Lexicon, Lawrence Nolan (ed.) Cambridge: CUP, 2016), 152–3.

⁵⁸ Third Meditation AT VII. 41; Secondly Set of Replies AT VII.165; Fifth Set of Replies AT VII.367; Axiom IV AT VII.165; Definition IV AT VII.161.

⁵⁹ For detailed discussion of this, but also of clarity and distinctness, see my op.cit. note 2, 2013/2016.

⁶⁰ Principles II.40.

⁶¹ Fifth Set of Replies AT VII.369.

⁶² AT VII.369.

⁶³ Kenny, op.cit. note 33: 41.

⁶⁴ Wilson, op.cit. note 33: 300. Cottingham, op. cit. note 17: 53. Schmaltz, (2006) op. cit. note 57. Radner, op. cit. note 17. Secada, Jorge, Cartesian Metaphysics: The Scholastic Origins of Modern Philosophy (Oxford: OUP, 2000), 81CrossRefGoogle Scholar. Hatfield, Gary, Descartes and the Meditations (London: Routledge, 2003), 164–5Google Scholar.

⁶⁵ CSM edition, vol.II fn2 AT VII.41, refers to Scholastic terminology and interprets ‘present formally or eminently’ in terms of properties, without pointing out Descartes’ non-adherence to it.

⁶⁶ O'Neill, op. cit. note 28: 230, 232–234, 232 fn20.

⁶⁷ AT VII.45 ‘Objective reality’ is what an idea presents its object as having – the aboutness or directedness of an idea. ‘Formal reality’ pertains to the object itself (including ideas).

⁶⁸ Broughton, Janet, ‘Adequate causes and Natural Change in Descartes’ Philosophy’ (Human Nature and Natural Knowledge: Essays Presented to Marjorie Grene. Donagan, A., Petovich, A.N. Jr., and Wedin, M.V. (eds) Dordrecht: Reidel, 1986), 107–127CrossRefGoogle Scholar: 118–119.

⁶⁹ O'Neill, op. cit. note 28: 233.

⁷⁰ Fifth Set of Objections AT VII.289. Part of their disagreement is over whether ‘reality or perfection’ should refer to material causes. Descartes rejects material causes, but also thinks that ‘it is unintelligible that perfection of form should ever pre-exist in a material cause’. (Fifth Set of Replies AT VII.366).

⁷¹ AT VII.80.

⁷² AT IXA 213. When discussing the human body, by ‘mechanical’ Descartes means organic, or the organism. Reference to a machine's interrelated parts is analogical, a way of explaining the organs of living entities whose unity (unlike that of machines) is not imposed by us. (Passions I:30 AT XI.351; and AT IV.576; CSMK:304) Des Chene, Dennis, Spirits and Clocks: Machine and Organism in Descartes (Ithaca: Cornell University Press, 2001: 68)Google Scholar, says it ‘was in the German Romanticism that the contrast of the organic and mechanical took on the value it still has, and the mechanical became coincident with the inert, the lifeless’.

⁷³ 21 May 1643 AT III.665–6; CSMK:218.

⁷⁴ Seventh Set of Objections with Replies AT VII.548; letter to Mersenne March 1642 AT III.544; CSMK:211.

⁷⁵ Wilson, op. cit. note 33: 209 & 211, thinks the union is arbitrary and consists in nothing more than correlations. Cottingham, op. cit. note 17: 127, says, some commentators ask how ‘can [the] notion [of union] be called ‘primitive’ if it is dependent on a union of two elements?’ There's a misunderstanding here: the union of the two presupposes the primary notion of union.

⁷⁶ Rule Twelve AT X.419.

⁷⁷ AT III.691.

⁷⁸ Principles I.10 AT VIIIA.8.

⁷⁹ January 1642 AT III.493 & (508); CSMK:206 & 209. See also letter to Regius of December 1641 (AT III.460–461; CSMK:200); letters to Princess Elizabeth 28 June 1643 (AT III.691; CSMK:226), and 21 May 1643 (AT III.665; CSMK:218). Fourth Set of Replies AT VII.227–228.

⁸⁰ AT VII.86.

⁸¹ January 1642 AT III.493; CSMK:206.

⁸² Alanen, Lilli, ‘Reconsidering Descartes’ Notion of the Mind–Body Union’, Synthese 106 (1996), 3–20CrossRefGoogle Scholar: 8, 9, 11, 13.

⁸³ AT VII.81. Schmaltz (2006), op. cit. note 57: 17, thinks because ‘we cannot know, simply by introspection, which qualities these [sensory] ideas represent’, Descartes ‘called these ideas confused and obscure’. Introspection has nothing to do with what these ideas are; moreover Descartes rejects the usefulness of introspection or ‘internal sense’. (AT VII.76).

⁸⁴ Third Set of Objections with Replies AT VII.176; inherence denotes dependence not spatial relation.

⁸⁵ AT VII.78.

⁸⁶ My metaphysical approach and the connection with self-consciousness, clearly distinguish my discussion of sensations from Schmaltz, Tad, ‘Descartes and Malebranche on Mind and Mind–Body Union’, Philosophical Review 101 (1992), 281–325CrossRefGoogle Scholar, and Rozemond, Marleen, Descartes’ Dualism (Harvard University Press, 1998)Google Scholar, chapter 6.

⁸⁷ Letter to Regius January 1642 AT III.(508); CSMK:209.

⁸⁸ This is consistent with the position that mind and body are really distinct and can exist without each other; hence ens per accidens is meant in this sense. How one entity, a person, can be constituted by two substances, or rather incomplete substances, but not as substantial form and matter, is something I discuss in my op. cit. note 2 2013/2016: 221–226.

⁸⁹ Letter to Regius December 1641 AT III.461; CSMK:200.

⁹⁰ Letter to Mesland 9 February 1645 AT IV.166; CSMK:243.

⁹¹ AT III.461.

⁹² AT VII.203. Brown, Deborah, ‘Understanding Interaction Revisited’, Debates in Modern Philosophy: Essential Readings and Contemporary Responses, Duncan, Stewart and LoLordo, Antonia (eds) (New York: Routledge, 2013), 54–64CrossRefGoogle Scholar: 55, states that in his reply to Gassendi, Descartes claims that ‘the mind uses a body’ contrary to his response to Arnauld. But Descartes is concerned with the mind's ‘power of moving the body’ (AT VII.389), of interacting with it, not of using it.

⁹³ Comments AT VIIIB.351.

⁹⁴ AT VII.81.

⁹⁵ It doesn't seem, as Williams thinks (op. cit. note 33: 289), Descartes was ‘tempted to read that phenomenological fact as a metaphysical one in relation to his task of the substantial union’.

⁹⁶ Letter to Descartes 6 May 1643 AT III.660.

⁹⁷ Fifth Set of Objections AT VII.343–4.

⁹⁸ 21 May 1643 AT III.665; CSMK:218.

⁹⁹ AT III.667.

¹⁰⁰ Fifth Set of Replies AT VII.390.

¹⁰¹ Letter to Regius January 1642 AT III.493 & (508); CSMK:206 & 209.

¹⁰² AT V.222; CSMK:357.

¹⁰³ AT VII.81.

¹⁰⁴ AT VII.78.

¹⁰⁵ Rule Twelve AT X 416.

¹⁰⁶ Letter to Hyperaspistes August 1641 AT III.424; CSMK:190.

¹⁰⁷ Optics AT VI.130.

¹⁰⁸ 21 May 1643 AT III.667–8; CSMK:219.

¹⁰⁹ Sixth Set of Replies AT VII.442.

¹¹⁰ Letter to Mersenne 26 April 1643 AT III.648; CSMK:216; emphasis added.

¹¹¹ AT III.694; CSMK:228; also section 2 above.

¹¹² I owe this suggestion to discussions with Peter J. King.

¹¹³ 28 June 1643 AT III.694; CSMK:228.

¹¹⁴ Garber, Daniel, ‘Understanding Interaction: What Descartes Should Have Said to Elisabeth’, Southern Journal of Philosophy 21 (1983), 15–32:16–17CrossRefGoogle Scholar, argues, although Descartes’ answer to Elizabeth is ‘philosophically serious’ and ‘perhaps defensible’, it is ‘not the answer that should have been offered’.

¹¹⁵ Garber, op. cit. note 34, denies the latter. His attribution of occasionalism, however, is unconvincing. Suffice to say that powers are constitutive of what it is to be a substance, corporeal or thinking, and thereby pertain to their modes.

¹¹⁶ Letter for [Arnauld] 29 July 1648 ATV.222; CSMK:358.

¹¹⁷ AT III.693.

¹¹⁸ AT III.691–692; CSMK:226–7.

¹¹⁹ AT III.693.

¹²⁰ AT III.692.

¹²¹ Descartes doubted the adequacy of experience for establishing scientia, but didn't deny it or its usefulness. Indeed, experience is restored in the Sixth Meditation, not least because he's not in the grip of the fantasy that reason unaided can give us knowledge of a world of corporeal objects, and he ridicules those who ignore experience and scientific experimentation. (Rule Five AT X.380).

¹²² I owe this suggestion to discussions with Peter J. King.

¹²³ AT X.419.

¹²⁴ AT VII.81.

¹²⁵ Sixth Set of Replies AT VII.444.

¹²⁶ AT III.693; CSMK:227; my italics.

¹²⁷ AT III.692.

¹²⁸ AT III.693.

¹²⁹ AT III.691.

¹³⁰ AT X.419; Principles I.10 AT VIIIA 8.

¹³¹ AT X.419.

¹³² AT VII.73.

¹³³ Letter to [Arnauld] 29 July 1648 AT V.222; CSMK:358.

¹³⁴ Optics AT VI.130.

¹³⁵ This paper has gone through several stages. My thanks are first to Stephen G. Williams for prompting me to address the mind-body relation, and offering various suggestions on the topic. An earlier draft of the paper was presented to the Work in Progress philosophy seminar at Worcester College, University of Oxford, in October 2016. I should like to thank Janine Guhler, Sabina Lovibond, Steven Methven, Martin Pickup, Kate Tunstall, Daniel Waxman, Stephen Williams for their valuable comments and encouragement. I gave a revised version of the paper at the Early Modern Philosophy Seminar, National University of Singapore, in November 2016. I should like to thank Cecilia Lim for inviting me, and the participants Loy Hui Chieh, Cecilia Lim, Hsueh Qu Ming, Saranindranath Tagore, Tang Weng Hong, and the audience at the Seminar for their valuable questions and comments. A much revised version was presented at the Scottish Seminar in Early Modern Philosophy VIII: April 2017, at the University of Edinburgh. I should like to thank the organiser Mogens Laerke, Pauline Phemister and Peter Millican for their comments, and the audience for their support and enthusiasm. I am indebted to Peter J. King for numerous discussions and encouragement throughout.