In contemporary, everyday language, the word \u201csubstance\u201d tends to be a generic term used to refer to various kinds of material stuff (\u201cWe need to clean this sticky substance off the floor\u201d) or as an adjective referring to something\u2019s mass, size, or importance (\u201cThat is a substantial bookcase\u201d).\u00a0 In 17th<\/sup> century philosophical discussion, however, this term\u2019s meaning is only tangentially related to our everyday use of the term.\u00a0 For 17th<\/sup> century philosophers, the term is reserved for the ultimate constituents of reality on which everything else depends.\u00a0 This article discusses the most important theories of substance from the 17th<\/sup> century: those of Descartes<\/a>, Spinoza<\/a>, and Leibniz<\/a>.\u00a0 Although these philosophers were highly original thinkers, they shared a basic conception of substance inherited from the scholastic-Aristotelian tradition from which philosophical thinking was emerging.\u00a0 In a general sense each of these theories is a way of working out dual commitments: a commitment to substance as an ultimate subject and a commitment to the existence of God as a substance.\u00a0 In spite of these systematic similarities between the theories, they ultimately offer very different accounts of the nature of substance.\u00a0 Given the foundational role that substance plays in the metaphysical schemes of these thinkers, it will not be surprising to find that these theories of substance underlie dramatically different accounts of the nature and structure of reality.<\/p>\n In thinking about 17th<\/sup> century accounts of substance we need to keep in mind that a concern with substance and its nature was nothing new to the period. In fact, philosophical thinking about the nature of substance stretches all the way back to ancient Greece.\u00a0 While the new philosophers of the 17th<\/sup> century were keen to make a break with the past and to tackle philosophical and scientific problems from new foundations, their views did not develop in an intellectual vacuum.\u00a0 Indeed, the scholastic-Aristotelian tradition of the day informed their thinking about substance in a number of ways, and contributed to a number of commonalities in their thought. Before looking at specific theories of substance, it is important to note four commonalities in particular.<\/p>\n Substance, Mode, Inherence<\/em><\/p>\n For the philosophers we will discuss, at the very deepest level the universe contains only two kinds or categories of entity: substances and modes.\u00a0 Generally speaking, modes are ways that things are; thus shape (for example, being a rectangle), color (for example, redness), and size (for example, length) are paradigm modes.\u00a0 As a way a thing is, a mode stands in a special relationship with that of which it is a way.\u00a0 Following a tradition reaching back to Aristotle\u2019s Categories<\/em>, modes are said to exist in, or inhere in, a subject.\u00a0 Similarly, a subject is said to have or bear modes.\u00a0 Thus we might say that a door is the subject in which the mode of rectangularity inheres.\u00a0 One mode might exist in another mode (a color might have a particular hue, for example), but ultimately all modes exist in something which is not itself a mode, that is, in a substance.\u00a0 A substance, then, is an ultimate subject.<\/p>\n Independence and Priority<\/em><\/p>\n The new philosophers of the 17th<\/sup> century follow tradition in associating inherence with dependence.\u00a0 They all agree that the existence of a mode is dependent in a way that the existence of a substance is not.\u00a0 The idea is that modes, as the ways that things are, depend for their existence on that of which they are modes, e.g. there is no mode of \u2018being 8\u20190 long\u2019 without there being a subject <\/em>that is 8\u20190 long.\u00a0 Put otherwise, the view is that the existence of a mode ultimately requires or presupposes the existence of a substance.\u00a0 This point is sometimes put by saying that substances, as subjects, are metaphysically prior to modes.<\/p>\n Degrees of Reality<\/em><\/p>\n In contrast to contemporary philosophers, most 17th<\/sup> century philosophers held that reality comes in degrees\u2014that some things that exist are more or less real than other things that exist.\u00a0 At least part of what dictates a being\u2019s reality, according to these philosophers, is the extent to which its existence is dependent on other things: the less dependent a thing is on other things for its existence, the more real it is.\u00a0 Given that there are only substances and modes, and that modes depend on substances for their existence, it follows that substances are the most real constituents of reality.<\/p>\n God Exists and is a Substance<\/em><\/p>\n Furthermore, each of the philosophers we will discuss maintains (and offer arguments on behalf of the claim) that God<\/a>\u00a0exists, and that God\u2019s existence is absolutely independent.\u00a0 It is not surprising then, given the above, that each of these philosophers holds that God is a substance par excellence<\/em>.<\/p>\n Descartes\u2019 philosophical system, including his account of substance was extremely influential during the 17th<\/sup> century.\u00a0 For more details see the IEP article Ren\u00e9 Descartes: Overview.\u00a0 Unlike Spinoza and Leibniz, however, Descartes\u2019 theory of substance was not the centerpiece of his philosophical system.\u00a0 Nonetheless, Descartes offered a novel theory of substance which diverged in important ways from the Scholastic-Aristotelian tradition.<\/p>\n It is sometimes said that Descartes gives two different definitions of substance, and indeed in the Principles<\/em> and Second Replies<\/em> he defines substance in distinct ways.\u00a0 We should not, however, see this as evidence that Descartes changed his mind.\u00a0 On the contrary, it is clear that for Descartes these definitions express two sides of a unified account of substance.<\/p>\n Let us begin with the definition he offers in his Principles of Philosophy <\/em>(I.51-52).\u00a0 There he defines \u2018substance\u2019 in terms of independence.\u00a0 He begins by making clear that there are really two different philosophical senses of the term (corresponding to two degrees of independence).\u00a0 For reasons that will become clear in a moment, let us distinguish the two senses by calling one Substance<\/em> and the other Created Substance<\/em>.\u00a0 Descartes\u2019 definitions can be paraphrased as follows:<\/p>\n Substance<\/em>: A thing whose existence is dependent on no other thing.<\/p>\n Created Substance<\/em>: A thing whose existence is dependent on nothing other than God.<\/p>\n Strictly speaking, for Descartes there is only one Substance<\/em> (as opposed to Created Substance<\/em>), since there is only one thing whose existence is independent of all other things: God.\u00a0 However, within the universe that God has created there are entities the existence of which depends only on God.\u00a0 These lesser substances are the ultimate constituents of the created world.<\/p>\n The definition of substance that Descartes offers in the Second Replies<\/em> (and elsewhere), ignores the distinction between God and creation and defines substance in a much more traditional way, claiming that a substance is a subject that has or bears modes, but is not itself a mode of anything else.\u00a0 This fits right in with his other comments about substance in the Principles<\/em>.\u00a0 Thus, he tells us that each created substance has exactly one attribute (Principles<\/em> I. 53).\u00a0 An attribute of a substance, Descartes explains, is its \u201cprinciple property which constitutes its nature and essence, and to which all its other properties are referred\u201d (Ibid.).\u00a0 A substance\u2019s attribute, consequently, dictates its kind since attributes \u201cconstitute\u201d a substance\u2019s nature and all and only those things of the same nature are of the same kind.\u00a0 Moreover, in claiming that all a substance\u2019s properties are referred through the substance\u2019s attribute, Descartes is claiming that a substance\u2019s attribute dictates the properties that a substance may have.<\/p>\n Descartes specifies two attributes: thought and extension.\u00a0 Consequently, there are at least two kinds of created substance\u2014extended substances and thinking substances.\u00a0 By \u2018extension\u2019 Descartes just means having length, breadth, and depth.\u00a0 More colloquially we might say that to be extended is just to take up space or to have volume.\u00a0 Whereas by \u2018thinking substance\u2019 Descartes just means \u2018mind\u2019.\u00a0 Although Descartes only ever discusses these two attributes, he never explicitly rules out the possibility of other attributes.\u00a0 Nevertheless, the tradition has interpreted Descartes as holding that there are only two kinds of created substance and it is for this reason that Descartes is often called a substance dualist<\/em>.<\/p>\n With this specification in hand we are in a better position to understand what Descartes means when he says that all a substance\u2019s properties are referred through the substance\u2019s attribute or \u201cprinciple property.\u201d\u00a0 Consider an extended substance, say, a particular rock.\u00a0 Among this rock\u2019s properties are shape and size; but having these properties presupposes the property of extension.\u00a0 Put otherwise, something cannot have a shape or a size without also being extended.\u00a0 Furthermore, the properties that the rock may have are limited to modifications of extension\u2014a rock cannot have the property of experiencing pain, for example, since the property of experiencing pain is not a way of being extended.\u00a0\u00a0 In general, we can say that for Descartes i) the attribute of a substance is its most general property, and that ii) every other property of a substance is merely a specification of, way of being, or mode of that attribute.<\/p>\n Given this account of the nature of substance, what substances exist?\u00a0 Descartes famously argues in Meditation Six<\/em> that human minds and bodies are really distinct\u2014that is, that they are each substances.\u00a0 Indeed, every individual consciousness or mind is a thinking substance.\u00a0 Furthermore Descartes treats bodies, including the objects of our everyday experience (chairs, trees, spoons, etc.) as extended substances. This makes sense. Extension is an attribute of substance, so it would seem to follow that anything that is extended (has the attribute of extension) is itself a substance.\u00a0 Moreover the parts of extended substances, as themselves extended, would seem to be extended substances for Descartes (see Principles<\/em> I. 60). Given that Descartes thinks that matter is infinitely divisible (Principles<\/em> II. 20)\u2014that each part of matter is itself extended all the way down\u2014it follows that there are an infinite number of extended substances.<\/p>\n We are thus left with the following picture of reality.\u00a0 The most real thing is God on which all other things depend.\u00a0 However, within the created realm there are entities that are independent of everything besides God.\u00a0 These are the created substances.\u00a0 Created substances come in two kinds\u2014extended substances and minds, and there is a plurality of both.<\/p>\n This brief summary of Descartes\u2019 account of substance raises a number of deeper questions and controversies.\u00a0 One central question that naturally arises is why Descartes thinks that extension and thought are the most general properties of substances.\u00a0 For a detailed discussion of Descartes\u2019 reasons see the IEP article\u00a0Ren\u00e9 Descartes: The Mind-Body Distinction.<\/em> This article will briefly consider the role of embodied human beings in Descartes metaphysics, what Descartes means in calling substances independent, and a related controversy concerning the number of material substances to which Descartes is entitled.<\/p>\n Embodied human beings fit uneasily into Descartes\u2019 metaphysics.\u00a0 As embodied, humans are composite beings; an embodied human being consists of a mental substance (our mind) and a physical one (our body), for Descartes.\u00a0 Descartes thinks that this composite being is, however, something over and above a mere aggregation.\u00a0 He writes in Mediation Six<\/em>: \u201cNature also teaches me\u2026that I am not merely present in my body as a sailor is present in a ship, but that I am very closely joined and, as it were, intermingled with it, so that I and the body form a unit<\/em>\u201d (my italics).\u00a0 In general, it is clear that Descartes thinks that embodied humans are exceptional beings in some regard, but how we should understand this mind\/body union and its place in Descartes\u2019 metaphysics has been a matter of some controversy among scholars.\u00a0 One of the more prominent disputes has been between those scholars who read Descartes as holding that embodied human beings are a distinct kind of created substance, and those scholars who do not.\u00a0 The former see Descartes as a substance trialist<\/em>, whereas the latter read him along traditional lines as a substance dualist.\u00a0 For trialist readings see Hoffman 1986 and Skirry 2005: Chapter 4).\u00a0 For recent defenses of substance dualism against trialist interpretations see Kaufman 2008 and Zaldivar 2011.<\/p>\n As we have seen, Descartes defines substance in terms of independence.\u00a0 This, however, is only a very general claim.\u00a0 In order to better understand Descartes\u2019 account of substance we need to have a better idea of the way in which substances are independent.\u00a0 On one hand, in his thinking about substance Descartes is working with the traditional conception of independence according to which a substance\u2019s existence is independent in a way that a mode\u2019s existence is not, since substances are ultimate subjects.\u00a0 Accordingly, let us say that substances are subject-independent.\u00a0 On the other hand, in his account of substance Descartes is also working with a causal sense of independence.\u00a0 After all, the reason that God is the only Substance<\/em> (as opposed to Created Substance<\/em>) is that all other things \u201ccan exist only with the help of God\u2019s concurrence\u201d (Principles<\/em> I.51), and Descartes understands this as the causal claim that all other things are God\u2019s creation and require his continual conservation.\u00a0 Consequently scholars have seen Descartes as holding that in general i) God is both causally and subjectively independent (God is not, after all, a mode of anything else), ii) created substances are causally independent of everything but God and subjectively independent, and iii) modes are both causally and subjectively dependent in that they both depend on God\u2019s continual conservation and on created substances as subjects. (See, for example, Markie 1994: 69; Rodriguez-Pereyra 2008: 79-80)<\/p>\n That created substances are causally independent of everything but God suggests a startling conclusion\u2014that despite what Descartes seems to say, bodies are not material substances, since they are not sufficiently independent.\u00a0 Bodies are causally dependent on other bodies in a host of different ways.\u00a0 For example, bodies come to be and are destroyed by other bodies: A person is the product of \u00a0their parents and could die as the result of getting hit by a car.\u00a0 Indeed, according to one scholarly tradition, there is only one material thing that satisfies Descartes\u2019 definition of created substance\u2014the material universe as a whole (see, for example, Cottingham 1986: 84-85).\u00a0 Again, following tradition we can call this view the Monist Interpretation<\/em>, and the opposing view that there are many material substances, the Pluralist Interpretation<\/em> (for a distinct view see Woolhouse 1993: 22-23).\u00a0 It would appear, then, that there is philosophical evidence of Monism; in other words, it would seem that Descartes\u2019 views about created substance commit him to thinking there can be only one material substance.\u00a0 Proponents of this interpretation claim that there is textual evidence as well, pointing to a passage in the Synopsis to the Meditations<\/em>.\u00a0 There Descartes writes:<\/p>\n [W]e need to recognize that body, taken in the general sense, is a substance, so that it too never perishes.\u00a0 But the human body, in so far as it differs from other bodies, is simply made up of a certain configuration of limbs and other accidents of this sort; whereas the human mind is not made up of any accidents in this way, but is a pure substance.<\/p>\n Monists read \u2018body, taken in the general sense\u2019 as referring to the material universe as a whole.\u00a0 Consequently, they see this passage as claiming that the material universe is a substance, but that the human body is not\u2014since it is made up on a configuration of limbs and accidents.\u00a0\u00a0 Assuming the monists are right, two questions immediately arise.\u00a0 First, if bodies are not substances, then what are they?\u00a0 Monists typically claim that bodies are modes.\u00a0 This makes sense: If bodies are not substances, they must be modes, given Descartes\u2019 ontology.\u00a0 Second, if Descartes does not think that bodies are substances, why does he so often talk as if they are?\u00a0 Monists answer that Descartes is speaking loosely in these contexts using the term \u2018substance\u2019 in a secondary or derivative sense of the term.<\/p>\n Pluralists have objected on a number of grounds.\u00a0 First, pluralists have challenged the monist\u2019s textual evidence, offering alternative readings of the Synopsis.\u00a0 Second, they have challenged the motivation of monism, pointing out that the monist interpretation requires a very strong conception of causal independence, and that it just isn\u2019t clear that this is Descartes\u2019 view. Third, pluralists note that although Descartes writes of bodies as substances on numerous occasions, he never clearly refers to them as modes.\u00a0 Last, pluralists have denied that Descartes could have held that bodies are modes noting that for Descartes i) parts of things are not modes of them and ii) bodies are parts of the material universe.\u00a0 Hoffman 1986 briefly raises each of these objections.\u00a0 For more lengthy discussions see Skirry 2005: Chapter 3 and Slowik 2001.<\/p>\n Spinoza\u2019s most important work is his Ethics Demonstrated in Geometric Order<\/em>\u2014henceforth the Ethics<\/em>. Spinoza worked on the text throughout the 1660s and 70s.\u00a0 By this time Descartes\u2019 philosophy had become widely read and indeed Spinoza\u2019s thinking was heavily influenced by it\u2014including his account of substance.\u00a0 Nevertheless, Spinoza\u2019s account diverges in important ways and leads to a radically different picture of the world.<\/p>\n Spinoza offers a definition of substance on the very first page of the Ethics<\/em>.\u00a0 He writes:\u00a0 \u201cBy substance I understand what is in itself and is conceived through itself… \u201c (E1d3).\u00a0 Spinoza follows Descartes (and the tradition) in defining substance as \u201cin itself\u201d or as an ultimate subject.\u00a0 Correspondingly, he follows the tradition in defining \u2018mode\u2019 as that which is had or borne by another; as Spinoza puts it a mode is \u201cthat which is in another\u2026\u201d (E1d5).\u00a0 For a discussion of the scholastic-Aristotelian roots of Spinoza\u2019s definition see Carriero 1995.\u00a0 Spinoza also follows Descartes in thinking that i) attributes are the principle properties of substance, ii) among those attributes are thought and extension, iii) all other properties of a substance are referred through, or are ways of being, that attribute, and iv) God exists and is a substance.\u00a0 Here the agreement ends.<\/p>\n The first obvious divergence from Descartes is found at E1P5.\u00a0 For Descartes there are many extended substances (at least on the pluralist interpretation) and many minds.\u00a0 Spinoza, however, thinks this is dead wrong.\u00a0 At E1P5 Spinoza argues that substance is unique in its kind\u2014there can be only one substance per attribute.\u00a0 This fact about substance (in combination with a number of other metaphysical theses) has far-reaching consequences for his account of substance.<\/p>\n It follows, Spinoza argues at E1P6, that to be a substance is to be causally isolated, on the grounds that i) there is only one substance per kind or attribute and ii) causal relations can obtain only between things of the same kind.\u00a0 Causal isolation does not, however, entail causal impotence.\u00a0 An existing substance must have a cause in some sense, but as causally isolated its cause cannot lie in anything outside itself.\u00a0 Spinoza concludes that substance \u201cwill be the cause of itself\u2026it pertains to the nature of a substance to exist\u201d (E1P7).\u00a0 Not only is a substance the cause of itself, but Spinoza later tells us that it is the immanent cause of everything that is in it (E1P18).\u00a0 Spinoza continues, in E1P8, by claiming that \u201cevery substance is necessarily infinite.\u201d\u00a0 In general Spinoza argues that if there is only one substance per attribute, then substance cannot be limited since limitation is a causal notion and substances are causally isolated.\u00a0 Last, Spinoza makes the case that substances are indivisible.\u00a0 He argues in E1P12-13 that if substance were divisible, it would be divisible either into parts of the same nature or parts of a different nature.\u00a0 If the former, then there would be more than one substance of the same nature which is ruled out by E1P5.\u00a0 If the latter, then the substance could cease to exist which is ruled out by E1P7; consequently substance cannot be divided.<\/p>\n Given this account of the nature of substance, what substances exist?\u00a0 From what has been said so far in the Ethics<\/em> it would be reasonable to suppose that, for Spinoza, reality consists of the following substances: God, one extended substance, one thinking substance, and one substance for every further attribute, should there be any.\u00a0 As it turns out, however, this is only partially right.\u00a0 It is true that Spinoza ultimately holds that God exists, that there is one extended substance, and one thinking substance.\u00a0 However, Spinoza denies that these are different<\/em> substances. The one thinking substance is numerically identical to the one extended substance which is numerically identical to God.\u00a0 Put otherwise, there is only one substance, God, and that substance is both extended and thinking.<\/p>\n Spinoza\u2019s official argument for this conclusion is at E1P14.\u00a0 He argues as follows: God exists (which was proven at E1P11).\u00a0 Given that God is defined as a being that possesses all the attributes (E1d6) and that there is only one substance per attribute (E1P5), it follows that God is the only<\/em> substance.\u00a0 For a detailed discussion of this argument, see the IEP article Spinoza: Metaphysics.<\/p>\n Given that God is the only substance and Spinoza\u2019s substance\/mode ontology, it follows that the material objects of our experience are not independently existing substances, but instead are modes of the one extended substance.\u00a0 So too, minds which Descartes had thought of as thinking substances are, according to Spinoza, modes of the attribute of thought.<\/p>\n We are thus left with the following picture of reality.\u00a0 Like Descartes, Spinoza holds that the most real thing is God on which all other things depend.\u00a0 However, there are no created substances. \u00a0God as the one substance has all the attributes, and consequently is both an extended substance and a thinking one.\u00a0 What Descartes had taken for created substances are actually modes of God.\u00a0 Nevertheless, Spinoza agrees with Descartes that the contents of reality come in two kinds\u2014modes of extension and modes of thought, and there is a plurality of both.<\/p>\n This account of the nature of substance yields a very different picture of the metaphysical structure of the world from Descartes (and from common sense).\u00a0 This article focuses on three questions in particular: (i) Why doesn\u2019t Spinoza accept created substances, (ii) How can a substance have more than one attribute, and (iii) How can a substance be indivisible as Spinoza suggests?<\/p>\n Spinoza will not countenance Descartes\u2019 distinction between Substance<\/em> and Created Substance<\/em> for a number of reasons.\u00a0 First, created substances are the causal products of God.\u00a0 However, substances are causally isolated, and so even if there were multiple substances, one could not be the causal product of the other.\u00a0 Second, as we have seen Descartes holds that despite their causal dependence on God, finite minds and bodies warrant the name \u2018substance\u2019 at least partially because such beings are ultimate subjects.\u00a0 Spinoza agrees that being an ultimate subject is an essential part of being a substance; the problem is that finite bodies and minds are not ultimate subjects.\u00a0 Spinoza\u2019s official grounds for this thesis are found in the arguments for E1P4 and 5.\u00a0 In general, Spinoza claims that what is distinctive of substances as ultimate subjects is that they can be individuated by attribute alone.\u00a0 According to Spinoza there are only two kinds of mark by which entities might be individuated\u2014by attribute and by mode.\u00a0 Substances as ultimate subjects cannot be individuated by mode, since subjects are metaphysically prior to modes.\u00a0 Two finite bodies, for example, are not individuated by attribute (since they are both extended) and so cannot be substances.<\/p>\n As we\u2019ve seen, for Descartes each substance has one\u2014and only one\u2014attribute.\u00a0 Spinoza\u2019s argument for substance monism, on the other hand, claims that there is a substance that possesses all the attributes.\u00a0 Spinoza justifies this move defensively; at E1P10s Spinoza claims that nothing we know about the attributes entails that they must belong to different substances, and consequently there is nothing illegitimate about claiming that a substance may have more than one attribute.\u00a0 Although this is Spinoza\u2019s stated defense, a number of scholars have claimed that Spinoza has the philosophical resources to make a much stronger argument.\u00a0 Specifically, they claim he has a positive case that, in fact, a substance possessing anything less than all the attributes (and hence, just one) is impossible.\u00a0 In brief Lin 2007 asks us to suppose that Spinoza is wrong, and that it is possible for there to be a substance that has fewer than all of the attributes (but at least one).\u00a0 Spinoza is a strong proponent of the Principle of Sufficient Reason (see, for example, E1P8s2) according to which there is an explanation for every fact.\u00a0 Given the PSR it follows that there is an explanation of why the substance in question fails to have all the attributes.\u00a0 However, any such explanation will have to appeal to the substance\u2019s existing attribute (or attributes).\u00a0 Attributes are conceptually independent however, and consequently one cannot appeal to an existing attribute to explain the absence of another.\u00a0 For a different but closely related version of this argument see Della Rocca 2002.<\/p>\n Unlike Descartes, Spinoza holds that substance is indivisible, and this raises a number of questions about the consistency of Spinoza\u2019s account of substance.\u00a0 For example, how is substance\u2019s indivisibility consistent with Spinoza\u2019s claims that (i) substance has many attributes which constitute its essence and (ii) that substance is extended?\u00a0 For a discussion of (i), see the IEP article Spinoza: Metaphysics.\u00a0 Here the focus is on (ii).<\/p>\n Spinoza\u2019s extended substance, or God considered under the attribute of extension, is normally understood as encompassing the whole of extended reality (though for an alternative see Woolhouse 1990).\u00a0 According to a philosophical tradition going back at least to Plato\u2019s Phaedo<\/em>, to be extended or corporeal is to have parts, to be divisible, and hence to be corruptible.\u00a0 Spinoza, however, holds that \u201cit pertains to the nature of substance to exist.\u201d\u00a0 Consequently, it would seem to follow that Spinoza cannot consistently hold that substance is extended.\u00a0 Spinoza was well aware of this argument and his official rejoinder is found in E1P15s.\u00a0 The problem with the argument is that it is \u201cfounded only on [the] supposition that corporeal substance is composed of parts.\u201d\u00a0 On its face, this is a confusing claim\u2014if extended or corporeal substance just is the whole of extended reality, it surely has parts.\u00a0 For example, there is the part of extension which constitutes an individual human body, a part which constitutes the Atlantic Ocean, a part that constitutes Earth, etc.\u00a0 Despite his wording, Spinoza is not denying that extended substance has parts in every sense of the term.\u00a0 Rather, Spinoza is especially concerned to counter the idea that his extended substance is a composite substance, built out of parts which are themselves substances, and into which it might be divided or resolved.\u00a0 This makes sense, since a) it is not having parts that is the problem, but being corruptible, and b) this account of extended substance as divisible into further extended substances is just what Descartes (one of the main influences on Spinoza\u2019s thought) seems to have held.<\/p>\n Spinoza makes his case in two ways in E1P15s.\u00a0 First, Spinoza points us back to the arguments at E1P12 and 13 for the indivisibility of substance.\u00a0 Second Spinoza offers a new argument that focuses specifically on extended substance, one that, interestingly, does not presuppose the prior apparatus of the Ethics<\/em>.\u00a0 In putting aside his own previous conclusions, Spinoza\u2019s apparent goal is to show that a view like Descartes\u2019 according to which any extended substance has parts which are themselves extended substances, fails on its own terms.\u00a0 In general, he argues as follows.\u00a0 Consider an extended substance, say a wheel of cheese.\u00a0 If the parts of this wheel are themselves extended substances, then it is\u2014at least in principle\u2014possible for one or more of the parts to be annihilated without any consequence for the other parts.\u00a0 The idea here is that because substances are independent subjects, the annihilation of one subject cannot have any consequence for the others.\u00a0 Suppose then that the middle of our wheel of cheese is annihilated; we are thus left with a \u201cdonut\u201d of cheese.\u00a0 The problem with this is that the hole in the cheese is measurable\u2014it has a diameter, a circumference, etc.\u00a0 In short, it is extended.\u00a0 However, we have supposed that the extended substance\u2014the subject of the extension\u2014in the middle was destroyed.\u00a0 We are thus left with an instance of attribute, extension, without a substance as its subject\u2014an impossibility by both Descartes\u2019 and Spinoza\u2019s standards.\u00a0 For detailed discussions of this argument see Huenemann 1997 and Robinson 2009.<\/p>\n Leibniz\u2019s views were informed by the accounts of both Descartes and Spinoza.\u00a0 In fact, Leibniz corresponded with Spinoza during the early 1670s and briefly visited with Spinoza in 1676.\u00a0 Unlike Spinoza, Leibniz did not write a single authoritative account of his metaphysical system.\u00a0 Not only that, but his metaphysical views changed in significant ways over his lifetime.\u00a0 Nevertheless, it is possible to identify a core account of the nature of substance that runs throughout his middle to later works (from the Discourse on Metaphysics<\/em> of 1686 through the Monadology<\/em> of 1714).<\/p>\n <\/p>\n Substances are independent and are ultimate subjects<\/em>.<\/p>\n Like Descartes, Leibniz thinks that God is the only absolutely independent thing, and that there are, in addition, created substances which are \u201clike a world apart, independent of all other things, except for God\u201d (Discourse on Metaphysics<\/em> \u00a78).\u00a0 Second, Leibniz explicitly agrees with Descartes, Spinoza, and the tradition in maintaining that substances are the ultimate bearers of modes or properties.\u00a0 He writes \u201cwhen several predicates are attributed to a single subject and this subject is attributed to no others, it is called an individual substance\u201d (Ibid.).<\/p>\n Substances are unities<\/em>.<\/p>\n To be a unity for Leibniz is to be simple and without parts, and so the ultimate constituents of reality are not composite or aggregative beings. That substances are simple has metaphysically significant consequences; Leibniz infers in the Principles of Nature and Grace<\/em> and elsewhere that \u201cSince the monads have no parts, they can neither be formed nor destroyed.\u00a0 They can neither begin nor end naturally, and consequently they last as long as the universe.\u201d\u00a0 A being comes to be naturally only as the result of a composition; an entity is destroyed naturally only through dissolution or corruption.\u00a0 Thus only composite entities are naturally generable or destructible.\u00a0 Leibniz emphasizes, however, that substances\u2019 unity and consequent simplicity is entirely consistent with the possession of and changes in modes or properties.<\/p>\n Substances are active<\/em>.<\/p>\n To say that a substance is active is to say not only that it is causally efficacious, but that it is the ultimate (created) source of its own actions. Thus he writes, \u201cevery substance has a perfect spontaneity\u2026that everything that happens to it is a consequence of its idea or of its being, and that nothing determines it, except God alone\u201d (DM \u00a732).\u00a0 Substances, in some sense, have their entire history written into their very nature.\u00a0 The history of each substance unfolds successively, each state causally following from the previous state according to laws.\u00a0 From this it follows that if we had perfect knowledge of a substance\u2019s state at a time and of the laws of causal succession, we could foresee the entire life of the substance.\u00a0 As Leibniz elegantly put the point in the Principles of Nature and Grace<\/em> \u201cthe present is pregnant with the future; the future can be read in the past; the distant is expressed in the proximate.\u201d<\/p>\n Substances are causally isolated<\/em>.<\/p>\n Like Spinoza, Leibniz holds both that substances are causally efficacious, and that their efficacy does not extend to other substances.\u00a0 In other words, although there is intra-substantial causation (insofar as substances cause their own states), there is no inter-substantial causation.\u00a0 Leibniz offers a number of different arguments for this claim.\u00a0 On some occasions he argues that causal isolation follows from the nature of substance. \u00a0If a state of a substance could be the causal effect of some other substance, then a substance\u2019s spontaneity and independence would be compromised.\u00a0 Elsewhere he argues that inter-substantial causation is itself impossible, claiming that the only way that one substance might cause another is through the actual transfer of accidents or properties.\u00a0 Thus Leibniz famously writes that substances \u201chave no windows through which something can enter or leave.\u00a0 Accidents cannot be detached, nor can they go about outside of substances\u201d (Monadology<\/em> \u00a77).\u00a0 For a more detailed discussion of Leibniz\u2019s views of causation see the IEP article Leibniz: Causation.<\/p>\n Although Leibniz agrees with Descartes that God is an infinite substance which created and conserves the finite world, he disagrees about the fundamental constituents of this world.\u00a0 For Descartes there are fundamentally two kinds of finite substance\u2014thinking substances or minds and extended substances or bodies.\u00a0 Leibniz disagrees; according to Leibniz (and this is especially clear in the later works) there are no extended substances.\u00a0 Nothing extended can be a substance since nothing that is extended is a unity.\u00a0 To be extended is to be actually divided into parts, according to Leibniz, and consequently to be an aggregate.\u00a0 The ultimate created substances, for Leibniz, are much more like Cartesian thinking substances, and indeed Leibniz refers to simple substances as \u201cminds\u201d or \u201csouls.\u201d\u00a0 This terminology can be confusing, and it is important to be clear that in using these terms Leibniz is not thereby claiming that all simple substances are individual human consciousnesses (although human consciousnesses are simple substances for Leibniz).\u00a0 Rather, there is a whole spectrum of simple substances of which human minds are a particularly sophisticated example.<\/p>\n We are thus left with the following picture of reality.\u00a0 God exists and is responsible for creating and continually conserving everything else.\u00a0 The ultimate constituents of reality are monads which are indivisible and unextended minds or mind-like substances.\u00a0 Although monads are causally isolated, they have properties or qualities that continually change, and these changes are dictated by the monad\u2019s nature itself.\u00a0 Leibniz\u2019s account of substance and his metaphysics in general, raise a number of questions.\u00a0 This article will take up three in particular.\u00a0 First, Leibniz\u2019s account of substance yields (in conjunction with a number of other metaphysical commitments) a picture of reality that diverges in significant ways both from common sense and from Descartes and Spinoza.\u00a0 How does our experience of an extended world of causal interaction fit into Leibniz\u2019s metaphysical picture?\u00a0 Second, that substances are unities is a crucial feature of Leibniz\u2019s account, and it is important to consider why Leibniz is so opposed to composite substances.\u00a0 Last, Spinoza and Leibniz offer very similar accounts of substance, yet end up with very different metaphysical pictures, and so this article will consider where Leibniz\u2019s account diverges from Spinoza\u2019s.<\/p>\n How does the world of our experience fit into Leibniz\u2019s account of reality?\u00a0 Our everyday experience is of extended objects causally interacting, but for Leibniz at the fundamental level there is no inter-substantial causation and there are no extended substances.\u00a0 How, then, is the world of our experience related to the world as it really is?<\/p>\n Let us begin with the apparent causal relations between things.\u00a0 Recall that, for Leibniz, monads are active and spontaneous.\u00a0 Each individual human mind is a monad, and this means that all of a human\u2019s experiences\u2014including their sensations of the world\u2014are the effects of their own previous states.\u00a0 For example, a person\u2019s sensation of a book\u2019s being on the desk is not caused by the book (or the light bouncing off the book, entering the eye,\u2026etc.) but is rather a progression in the unfolding of the history written into the person\u2019s nature.\u00a0 Although a monad\u2019s life originates from its nature alone, God has created the world so that the lives of created monads perfectly correspond.\u00a0 Leibniz writes in A New System of Nature<\/em>,<\/p>\n God originally created the soul (and any other real unity) in such a way that everything must arise for it from its own depths\u2026yet with a perfect conformity relative to external things…There will be a perfect agreement among all these substances, producing the same effect that would be noticed if they communicated through the transmission of species or qualities, as the common philosophers imagine they do.<\/p>\n Thus, when Katie walks around the corner and sees Beatrice, and Beatrice sees Katie, they do so because it was written into Katie\u2019s very nature that she would see Beatrice, and into Beatrice\u2019s nature that she would see Katie.\u00a0 This is Leibniz\u2019s famous doctrine of pre-established harmony.\u00a0 For more see the IEP article Leibniz: Metaphysics.<\/p>\n How does our experience of an extended world of bodies arise? To start, Leibniz certainly doesn\u2019t think that bodies are built out of, or are composites of, monads.\u00a0 Thus he writes in his Notes on Comments by Michel Angelo Fardella<\/em>, \u201cjust as a point is not a part of a line\u2026so also a soul is not a part of matter.\u201d\u00a0 Instead in many cases Leibniz characterizes bodies as phenomena or appearances.\u00a0 He writes in an oft-cited passage to DeVolder:<\/p>\n [M]atter and motion are not substances or things as much as they are the phenomena of perceivers, the reality of which is situated in the harmony of the perceivers with themselves (at different times) and with other perceivers.<\/p>\n Leibniz seems to be saying here and elsewhere that bodies are merely appearances (albeit shared appearances) that do not correspond to any mind-independent reality, and indeed a number of scholars have claimed that this is Leibniz\u2019s considered view (see, for example, Loeb\u00a0 1981: 299-309).\u00a0 In other texts however Leibniz claims that bodies result from, or are founded in, aggregates of monads, and this suggests that bodies are something over and above the mere perceptions of monads.\u00a0 In general, scholars have offered interpretations that attempt to accommodate both sets of texts and which see bodies as being aggregates of monads that are perceived as<\/em> being extended.\u00a0 There is a great deal of debate, however, about how such aggregates might ultimately be related to bodies and their perception (for one account see Rutherford 1995b: 143-153).<\/p>\n Leibniz thinks composite beings are excluded as possible substances on a number of grounds. \u00a0First, no composite is (or can be) a unity, since according to Leibniz there is no way that two or more entities might be united into a single one.\u00a0 He famously illustrates this claim by appealing to two diamonds.\u00a0 He writes in his Letters to Arnauld<\/em>:<\/p>\n One could impose the same collective name for the two\u2026although they are far part from one another; but one would not say that these two diamonds constitute a substance\u2026Even if they were brought nearer together and made to touch, they would not be substantially united to any greater extent\u2026 contact, common motion, and participation in a common plan have no effect on substantial unity.<\/p>\n In general, there is no relation that two or more entities might be brought into that would unify them into a single being.<\/p>\n A second and perhaps even deeper problem with composites is that according to Leibniz they cannot be ultimate subjects. He writes, again in the Letters to Arnauld<\/em>, \u201cIt also seems that what constitutes the essence of a being by aggregation is only a mode of things of which it is composed.\u00a0 For example, what constitutes the essence of an army is only a mode of the men who compose it.\u201d\u00a0 Leibniz\u2019s claim is that no aggregate is a substance because aggregates are modes or states of their parts, and no mode is an ultimate subject.\u00a0 This leaves us with a question, however: Why does Leibniz think that aggregates are mere modes or states of their parts?\u00a0 In his influential book R.C. Sleigh (1990: 123-124) makes the case that Leibniz\u2019s grounds for thinking aggregates are modes is that aggregates are semantically and ontologically dispensable.\u00a0 That is, everything that is true of an aggregate can be expressed by attributing various modes to the parts, all without appealing to the aggregate itself.\u00a0 This tells us that that all of an aggregate\u2019s purported modes are in fact modes of the parts, and that consequently the aggregate is not an ultimate subject.\u00a0 Given a substance\/mode ontology, it follows that to the extent that aggregates exist, they must be modes.<\/p>\n Although Spinoza and Leibniz offer very different pictures of the structure of reality, their respective accounts of substance overlap in important ways: Both agree that to be a substance is to be at least i) an ultimate subject, ii) causally isolated but causally efficacious, and iii) indivisible.\u00a0 Indeed, a number of scholars have suggested that Leibniz briefly adopted or was at least tempted by a Spinozistic metaphysics early in his philosophical career (see, for example, the discussion in Adams 1994: 123-130).\u00a0 Even later in life Leibniz seems to have held Spinoza\u2019s views in high regard saying in a Letter to Louis Bourguet<\/em> that \u201c[A]ccording to Spinoza\u2026there is only one substance.\u00a0 He would be right if there were no monads.\u201d\u00a0 Given this it is worth considering where Leibniz breaks with Spinoza and why.<\/p>\n Although they differ in a number of important ways, perhaps the most prominent difference between the metaphysics of Spinoza and Leibniz is that Leibniz holds that reality is split into two: God and creation.\u00a0 God is a substance and He produces finite substances\u2014created monads.\u00a0 This signals a break from Spinoza in at least two significant ways.\u00a0 First, it means that Leibniz\u2019s agreement with Spinoza about the causal isolation of substances applies only to created substances; although for Leibniz God is a substance, He is not causally isolated.\u00a0 Recall that at least one of Leibniz\u2019s reasons for denying inter-substantial causation is that it would require the actual transfer of properties or accidents, and that such a transfer is impossible.\u00a0 Jolley (2005) makes the case that, for Leibniz, God\u2019s causal activity is of a different kind.\u00a0 God does not produce effects in a metaphysically intolerable way, and consequently, God need not be causally isolated.<\/p>\n Second, Leibniz holds, in contrast to Spinoza, that created substances are ultimate subjects.\u00a0 Leibniz is very explicit about his objection to Spinoza on this score.\u00a0 Although he agrees that substances require individuation, he holds that Spinoza\u2019s proof at E1P5 that there can be only one substance per nature or attribute is unsound.\u00a0 Furthermore Leibniz holds that Monads can be individuated, ultimately claiming in the Monadology<\/em> that \u201cMonads\u2026are\u2026differentiated by the degrees of their distinct perceptions.\u201d<\/p>\n Looking back, we might see Descartes, but especially Spinoza and Leibniz, as working through the metaphysical consequences of holding that substances are ultimate subjects.\u00a0 More generally, we can see these theories of substance as different ways of trying to reconcile the notion of substance as an ultimate subject with a commitment to God\u2019s existence and independence.<\/p>\n Epistemological considerations led prominent late 17th<\/sup> and 18th<\/sup> century philosophers to abandon such questions, and to give substance a much more modest position in their metaphysical systems.\u00a0 John Locke, for example, holds that there are substances and that they are ultimate subjects, but is wary of drawing any further conclusions.\u00a0 As Locke famously claims, \u201cif any one will examine himself concerning his Notion of pure Substance in general<\/em>, he will find he has no other Idea of it at all, but only a Supposition of he knows not what support of such Qualities…commonly called Accidents\u201d (EHU<\/em> 2.23.2).\u00a0 David Hume goes further claiming that it is not within our power to know the ultimate structure of reality, and further that our idea of a substance as a subject is merely the result of our imagination: \u201cThe imagination is apt to feign something unknown and invisible, which it supposes to continue the same under all these variations; and this unintelligible something it calls a substance\u201d (Treatise<\/em> 1.4.3).\u00a0 Humean skepticism about substance (and about metaphysics more generally) survives in one form or another to the present day.<\/p>\n Of course not everyone agrees with this tradition, and the nature of substance has been a question that many contemporary philosophers have taken up\u2014albeit from different starting points than Descartes, Spinoza, and Leibniz.\u00a0 Unlike the 17th<\/sup> century, in contemporary philosophical use the term \u2018substance\u2019 is not necessarily intended to refer to the ultimate constituents of reality (although it may).\u00a0 Rather the term is usually taken to refer to what are sometimes called \u201cconcrete particulars\u201d, that is, to individual material things or objects.\u00a0 Furthermore, among contemporary philosophers there is nothing like the consensus that we find among the 17th<\/sup> century philosophers regarding ontology, dependence, reality, and God.\u00a0 Thus, it is commonly held that there are categories of reality beyond substance and mode (or property), perhaps most prominently events or processes.\u00a0 Many philosophers have questioned both the relation of inherence and the connection between inherence and ontological dependence. Bundle-theories of substance, for example, deny that substances are subjects at all\u2014they are merely bundles or collections of properties. \u00a0Furthermore, most contemporary philosophers deny that it makes sense to talk about degrees of reality: Things are either real or not.\u00a0 Last, and perhaps most obviously, contemporary philosophers no longer agree that God exists and is a substance.\u00a0 For a contemporary effort to offer an account of substance that is in the spirit of 17th<\/sup> century discussions, see Hoffman and Rosenkrantz 1997.<\/p>\nTable of Contents<\/h3>\n
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<\/a>1. 17th Century Theories of Substance: A Shared Background<\/h2>\n
<\/a>2. Descartes<\/h2>\n
<\/a>a. Descartes\u2019 Account of Substance<\/h3>\n
<\/a>b. What Substances are There?<\/h3>\n
<\/a>c. Are Embodied Human Beings Substances?<\/h3>\n
<\/a>d. How is Substance Independent?<\/h3>\n
<\/a>e. How Many Material Substances?<\/h3>\n
<\/a>3. Spinoza<\/h2>\n
<\/a>a. Spinoza\u2019s Account of Substance<\/h3>\n
<\/a>b. What Substances are There?<\/h3>\n
<\/a>c. Why doesn\u2019t Spinoza Countenance Created Substance?<\/h3>\n
<\/a>d. How Can a Substance Have More than One Attribute?<\/h3>\n
<\/a>e. An Extended and Indivisible Substance?<\/h3>\n
<\/a>4. Leibniz<\/h2>\n
<\/a>a. Leibniz\u2019s Account of Substances<\/h3>\n
<\/a>b. What Substances are There?<\/h3>\n
<\/a>c. Experience and Reality<\/h3>\n
<\/a>d. What is Wrong with Composite Beings?<\/h3>\n
<\/a>e. Leibniz and Spinoza<\/h3>\n
<\/a>5. 17th Century Theories of Substance in Perspective<\/h2>\n
<\/a>6. References and Further Reading<\/h2>\n
<\/a>a. Primary Texts in English<\/h3>\n
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<\/a>b. Secondary Texts<\/h3>\n
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