Leibniz on the Nature of Phenomena Stephen Puryear (Raleigh) 1. Introduction The category of phenomenon or appearance is one of the fundamental categories in Leibniz's ontology. But scholars disagree about the precise nature of phenomena in his thought. Many texts seem to portray phenomena as a kind of mental content, or perhaps a (merely) intentional object, something which has its being only within a perceiving subject. 1 Donald Rutherford calls this the "narrower and more usual" conception of phenomenon. 2 But Leibniz's doctrines about body have led some scholars to ascribe to him a broader, less mentalistic, conception of phenomena (e.g., one on which phenomena depend on perception for their existence, but do not have their being only in the mind). In this paper, I will consider three such doctrines: first, that bodies, which are phenomena, presuppose unities or simple substances; second, that bodies are aggregates of monads; and third, that bodies derive or borrow their reality from their simple constituents. After briefly summarizing the evidence for the narrow conception of phenomenon, I will argue that these doctrines can be harmonized with that conception, and thus that they give us no reason to ascribe to him the other, less mentalistic conception of phenomenon. 2. Phenomena as Mental Contents Many of Leibniz's statements about phenomena suggest that he conceives of them as a kind of mental content, something having their being only in the mind. Herewith a brief summary of the main lines of evidence: First, Leibniz often describes phenomena as, in one way or another, internal to the soul or perceiver. He characterizes them as "consequences of our being", which "maintain a certain order [...] in conformity with the world which is in us" and which "correspond" with the phenomena of others. 3 He contrasts the view that "there is extension outside of us" with the view that extension "is only a phenomenon, as is color". 4 He speaks of "the varied phenomena or appearances which exist in my mind". 5 He says our "inner sensations" or "internal perceptions in the soul" are "only a sequence of phenomena relating to external things, or really [...] appearances or systematic dreams, as it were". 6 He describes phenomena as "internal" and "quite independent of outside things which might make them arise in the soul", 7 as "internal", "in the soul", and 1 R. M. Adams: Leibniz: Determinist, Theist, Idealist. Oxford 1994, p. 219. 2 D. Rutherford: "Leibniz and the Problem of Monadic Aggregation", in: Archiv für Geschichte der Philosophie 76/1, pp. 65–90, here pp. 69–70. 3 Discours de métaphysique; A VI, 4, 1549–1551. 4 Leibniz to Foucher, 1686; A II, 2, 91. 5 De modo distinguendi phaenomena realia ab imaginariis; GP VII, 319. 6 Système nouveau de la nature et de la communication des substances, aussi bien que de l'union qu'il y a entre l'âme et le corps; GP IV, 484. 7 Système nouveau pour expliquer la nature des substances et leur communication entre elles, aussi bien que l'union de l'âme avec le corps; GP IV, 476–477. 2 "modifications of our souls", 8 and as appearances that are "different in different observers" and "nothing outside of perceptions". 9 Examples of this sort can easily be further multiplied. Second, Leibniz frequently likens phenomena to dreams. We have already seen this in the passage just quoted from the Système nouveau, where Leibniz characterizes phenomena as "appearances or systematic dreams" (GP IV, 484). To give just one more example, he says in the aforementioned Entretien that phenomena are distinguished from dreams "by their interconnections" (GP VI, 590). 10 In other words, the point in these and many other passages is that phenomena are like dreams in being internal to the soul, but differ from them in being more coherent. This goes hand-in-hand with the conception of phenomena as internal to the soul. Third, in several texts Leibniz construes phenomena as beings of perception or of the imagination, which he likens to beings of reason (GP II, 96; GP VI, 586). Here is one example, once again from the Entretien: "[B]ody is not a true unity; it is only an aggregate, what the schools call one by accident, an assemblage like a flock; its unity arises from our perception. It is a being of reason, or rather of imagination, a phenomenon." (GP VI, 586) This is telling because in the schools, an ens rationis had typically been understood, following Suárez, as "that which has being only objectively in the intellect". 11 Leibniz's point would appear to be that phenomena have their being only within the faculties of perception and imagination of mind-like, perceiving substances, that is, monads. Fourth, Leibniz frequently says that aggregates have their unity in perception, and that this makes them phenomena. But he also holds that unity and being are convertible or interchangeable. 12 By this he means that 'unity' and 'being' can be substituted for one another without affecting the truth-value of a claim. Hence, it follows from the fact that aggregates have their unity in the mind that they also have their being in the mind. As Leibniz argues in the Nouveaux essais, "Beings by Aggregation have only a mental unity, and consequently their being is also in a way mental, or phenomenal, like that of a rainbow" (A VI, 6, 146). Finally, Leibniz holds that imaginary phenomena such as the centaur or the golden mountain have their being only in the mind (see, e.g., GP VII, 319). But real phenomena differ from imaginary phenomena only in their reality, that is, either because they cohere with other phenomena or because they have a foundation in some external 8 Entretien de Philarète et Ariste; GP VI, 589–591. 9 Leibniz to Remond, July 1714; GP III, 622–623. 10 For other such texts, see A VI, 4, 1622; A II, 2, 186; A II, 2, 201–202; GP IV, 473; GP IV, 484; GP IV, 476–477; GP IV, 519; GP IV, 569; GP VI, 494; A VI, 6, 374–375; GP VII, 467–468; GP VI, 404; GP VI, 589–590; GP III, 567n; GP III, 623; GP II, 435–436; GP II, 504. 11 J. Doyle (ed.): Francisco Suárez, S. J.: On Beings of Reason, Metaphysical Disputation LIV, Milwaukee 1994, disp. 54, sec. 1, no. 6. On Leibniz's familiarity with Suárez and his Disputationes, see R. Ariew: "Descartes and Leibniz as Readers of Suárez: Theory of Distinctions and Principle of Individuation", in: B. Hill/H. Lagerlund (eds.): The Philosophy of Francisco Suárez, Oxford 2012, pp. 38–53, here pp. 46–54. 12 Cf. GP II, 97; GP II, 300; GP II, 304. 3 reality. But neither of these kinds of reality move the phenomenon outside the mind. So real phenomena also have their being only in the mind. These fives lines of evidence all converge on the conclusion that phenomena are something like mental contents or merely intentional objects. Though one might perhaps find a few texts here and there that suggest a less mentalistic conception of phenomenon, the vast majority of the most explicit evidence clearly points to the narrow conception. My aim in what follows will be to show that, contrary to what some have suggested, this narrow conception is compatible with several of Leibniz's most prominent doctrines about phenomena. 3. Phenomena and Presupposition I begin with the doctrine that bodies, which are phenomena, presuppose unities or simple substances. My foil here will be Richard Arthur, who discusses Leibniz's argument for this doctrine at length. 13 According to Arthur, this argument lies "At the heart of Leibniz's metaphysics". 14 As he characterizes it, the argument runs like this: 1. Every body is actually divided into other bodies. 2. Therefore, every body is an infinite aggregate. (from 1) 3. The reality of an aggregate reduces to the reality of the unities it presupposes. 4. Hence, every real body presupposes an actual infinity of real unities. (from 2, 3) 5. Some bodies are real. 6. Thus, there are an actual infinity of real unities (i.e., monads). (from 4, 5) Later in his essay, Arthur considers the sense in which bodies are phenomena. He admits that "an infinite aggregate, insofar as it is distinct from its constituents, is purely phenomenal." But he hastens to add: "But this hardly supports the idealist/phenomenalist reading that Robert Adams and others have proposed. For if bodies are, ultimately, phenomena in the sense of mental phenomena of perceivers, this undercuts the argument given here for positing monads in the first place. The presupposition argument described above would simply collapse, and with it the argument for the infinite multiplicity of monads." (Arthur: "Presupposition", p. 103) Arthur's point here is this. Even if an infinite aggregate, considered as something distinct from its constituents, is a pure or mental phenomenon, that cannot be what is meant by an infinite aggregate in the presupposition argument. For a phenomenon in the mind, even if an infinite aggregate, does not presuppose real unities. Instead, the infinite aggregates adverted to in Leibniz's argument must be, not distinct from their constituents, but nothing more than those constituents: "the body, insofar as it is a real phenomenon, is simply those substances". 15 In other words, an infinite aggregate in the relevant sense must be nothing more than (many) monads. Only then does the argument work. Hence, even if Leibniz does countenance "pure phenomena"-i.e., phenomena in the sense of 13 R. T. W. Arthur: "Presupposition, Aggregation, and Leibniz's Argument for a Plurality of Substances", in: Leibniz Review 21, pp. 91–115. 14 Arthur: "Presupposition", p. 91. 15 Arthur: "Presupposition", p. 108. 4 mental contents-we must also ascribe to him a less mentalistic conception of phenomenon, which applies even to what is nothing more than many substances. In response, I want to suggest that there is another way of viewing the presupposition relation in Leibniz's argument, one which is compatible with bodies being phenomena in the sense of mental contents. My suggestion is simply that a body might presuppose real unities for its own reality in the sense that a phenomenon presupposes some external (i.e., substantial) foundation for its reality. Admittedly, Leibniz sometimes allows that a phenomenon could have a kind of reality even in the absence of an external foundation, namely, in virtue of cohering with other phenomena. 16 But in addition to this weaker notion of reality, Leibniz ascribes a stronger kind of reality to phenomena, which they possess in virtue of having a foundation in substances. So if bodies are phenomena in the mind, and they have this stronger kind of reality, then it would follow that they presuppose real unities or monads for this reality, just as the presupposition argument requires. In order for this understanding of the presupposition argument to be convincing, I need to address two additional concerns. First, Leibniz thinks of a body as an aggregate of the real unities it presupposes. So I need to explain how a phenomenon in the mind could be understood as an aggregate of extramental monads, or in other words, how those monads could be constituents of a phenomenon in another monad. In other words, I need to show that a body can be both an aggregate of monads and a phenomenon in the mind. I will undertake to do that in Section 4. Further, the presupposition argument says that the reality of an aggregate (i.e., a body) is really just the reality of its constituents. So I need to make sense of the idea that a phenomenon in the mind could have a reality that is really just the reality of substances which serve as its external foundation. I will undertake to do that in Section 5. 4. Phenomena and Aggregates Leibniz scholars have long wrestled with the problem of how to reconcile Leibniz's belief that bodies are aggregates of monads with his claim that they are phenomena. Many commentators have concluded that these doctrines cannot be reconciled if bodies are understood to be phenomena in the narrow sense of a mental content. Thus some, such as Donald Rutherford, have posited a broader notion of phenomenon for this purpose. 17 Others have bit the bullet and accepted that these doctrines are irreconcilable. 18 In contrast, I want to suggest that we can indeed make sense of the claim that bodies are aggregates of monads, even on the assumption that they are also phenomena in the sense of mental contents. 16 Cf. Adams: Leibniz, pp. 259–260. 17 D. Rutherford: "Phenomenalism and the Reality of Body in Leibniz's Later Philosophy", in: Studia Leibnitiana 22/1 (1990), pp. 11–28, here pp. 18–19; D. Rutherford: "Leibniz and the Problem of Monadic Aggregation", in: Archiv für Geschichte der Philosophie 76/1 (1994), pp. 65–90, here pp. 69–70; D. Rutherford: "Leibniz as Idealist", in: Oxford Studies in Early Modern Philosophy 4 (2008), pp. 141– 190, here p. 181. 18 G. Hartz: Leibniz's Final System: Monads, Matter, and Animals, London 2007; D. Garber: Leibniz: Body, Substance, Monad, Oxford 2009. 5 A number of scholars, especially Rutherford, have pointed out that Leibniz appears to have a technical conception of aggregate that he defines in terms of the idea of an immediate requisite. 19 In his terminology, A is an immediate requisite of B just in case (i) A is prior in nature to B and (ii) positing B immediately presupposes positing A. To say that positing B immediately presupposes positing A is to say that, having posited B, we must by that very fact be understood to have posited A. In effect, what this means is that it is metaphysically (or perhaps even conceptually) impossible to posit B without also positing A. Finally, Leibniz defines an aggregate of Fs, in effect, as a thing that has those Fs as immediate requisites (at a given level of analysis). Hence, in his technical terminology, to speak of a body as an aggregate of monads is just to say that those monads are immediate requisites of the body, or in other words, that the body presupposes those monads with metaphysical (or perhaps even conceptual) necessity. As for the precise respect in which a thing presupposes or depends on its immediate requisites, Leibniz shows a good deal of flexibility. In some texts he characterizes it as a dependence of being (A VI, 4, 871), in others a dependence of existence (A VI, 4, 563, 650). In one he even suggests a dependence of reality (A VI, 4, 990). Given Leibniz's technical definition of aggregate, then, the question before us is really just the question whether a phenomenon in the mind can be said to immediately presuppose monads in one (or more) of these respects. Let us start with being. If bodies are phenomena in the sense of perceptual contents, then they have their being in the perceiving subject. So they obviously do not depend on other monads for their being. If an immediate requisite is always that which a thing immediately presupposes for its being, then a phenomenon in this sense could not be an aggregate of monads, even in Leibniz's technical sense. What about existence and reality? In the first place, we can indeed make good sense of the idea that phenomena immediately presuppose monads for their reality. For, on Leibniz's view, phenomena, though in themselves imaginary, can be said to acquire a kind of reality in virtue of having a foundation in some external, substantial realities. Phenomena with this sort of reality will therefore depend on their foundational monads for that reality, even if they have their being only in another monad. Further, this dependence will be not merely physical but metaphysical, just as Leibniz requires for his technical definition of aggregate, since it is metaphysically (and perhaps even conceptually) impossible for a phenomenon to be real in this sense without having a foundation in substances. With respect to reality, then, a phenomenon in the mind can indeed be understood to have extramental monads as its immediate requisites. Existence is a trickier case. Many commentators have tended to lump existence together with being, as if they were the same. However, I want to suggest that existence is something more than mere being. More exactly, I want to suggest that, on Leibniz's view, existence may be defined as real being. So, in other words, to say that X exists, 19 D. Rutherford: "Leibniz's 'Analysis of Multitude and Phenomena into Unities and Reality'", in: Journal of the History of Philosophy 28/4 (1990), pp. 525–552; Rutherford: "Leibniz as Idealist". See also S. Di Bella: "Leibniz's Theory of Conditions: A Framework for Ontological Dependence", in: Leibniz Review 15 (2005), pp. 67–93; M. Mugnai: "Leibniz and 'Bradley's Regress'", in: Leibniz Review 20 (2010), pp. 1–12; Arthur: "Presupposition". 6 whether X is a substance or a phenomenon, is just to say that X has being (or is a being) and that X is (in some sense) real. On this view, something that has its being in my mind, such as a centaur or the golden mountain, would not exist, because it is not also real. But if something having its being in my mind were in a sense real, it could be said to exist. Thus, a rainbow that has a foundation in some external reality could be said to exist, on this view, even if it has its being only in the mind. If this is in fact the way Leibniz thought about existence, then it follows that a phenomenon in the mind can also be understood to presuppose its foundational monads for its existence. Just as a phenomenon immediately presupposes those monads for its reality, it would also immediately presuppose those monads for its existence. Hence, there are at least two important respects in which a phenomenon's foundational monads can be considered its immediate requisites; and for this reason, we can indeed make good sense of the idea that a phenomenon in the mind is an aggregate of monads outside that mind. 5. Phenomena and Reality Derivation I come now to the problem of reality derivation. Leibniz claims that bodies, as aggregates, have a reality that they borrow or derive from their constituents. In some passages he even goes so far as to say that there is nothing more to the reality of the aggregate than the reality of its ingredients. But he also claims that bodies, and aggregates, are phenomena. According to some commentators, however, a phenomenon in the mind could not have a reality that it derives from the monads which are the ultimate constituents of a real body. Thus, in a recent discussion of Leibniz's borrowed reality argument, Samuel Levey remarks: "[G]iven the claim [...] that aggregates borrow their reality from their constituents, I think we must understand 'consists of' to be a fairly strong relation of reducibility or of the exhaustiveness of the contribution of the ingredients to the thing that consists of them. Roughly, if x consists of the ys, then there is nothing more to x than the ys."20 On this view, an aggregate can borrow its reality from its constituents only if it is (roughly) nothing more than those constituents, that is, not an entity in its own right but just those constituents. Hence, if bodies are both aggregates of monads and also phenomena, then they must be phenomena not in the narrow sense of a mental content, which would be something more than its foundational monads, but in some less mentalistic sense. It seems to me that Levey takes Leibniz's talk of reality derivation [mutuor, obtenir] rather literally, as if the reality of an aggregate's constituents were somehow transmitted from them to the unity which arises out of them. Since it's hard to see how a thing's reality could be transmitted to a distinct entity, this literal understanding of reality derivation supports Levey's thesis that an aggregate is nothing more than its constituents. But suppose we take the talk of reality derivation less literally. In particular, suppose we take Leibniz's point to be just that the aggregate obtains its reality from its constituents in the sense that it obtains what reality it has in virtue of the reality of those constituents. In 20 S. Levey: "On Unity, Borrowed Reality and Multitude in Leibniz", Leibniz Review 22 (2012), pp. 97–134, here pp. 104–105. For a similar line on reality derivation, see Rutherford: "Leibniz as Idealist", pp. 148, 160–161, 184. 7 other words, suppose the idea is just that an aggregate's reality depends immediately upon the reality of those constituents. So understood, it does seem possible for an aggregate of monads to be a phenomenon in the mind and to have a reality that it derives from its constituents, that is, from the phenomenon's foundation. For, as we have seen, a phenomenon in the mind can be said to acquire a kind of reality in virtue of having a foundation in some external realities, that is, monads, and thus it depends immediately on these monads for its reality. We may even suppose that the reality an aggregate acquires is something like an image or reflection of the reality of its constituents. In this way, we can give a good sense to the claim that an aggregate's reality is nothing more than the reality of its aggregata. 6. Conclusion In many texts, Leibniz speaks of phenomena as a kind of mental content, something having its being only in the perceiver: they are internal to the soul, like well-ordered dreams, beings of perception or of the imagination, and so forth. I have argued that bodies can be phenomena in this narrow sense, even while they (1) presuppose monads, (2) are aggregates of these monads, and (3) have a reality that is derived from, indeed is nothing more than, the reality of those monads. Hence, I conclude that these doctrines about Leibnizian bodies give us no reason to augment the narrow conception of phenomenon with a broader, less mentalistic one. Leibniz, we may plausibly suppose, consistently conceives of phenomena as a kind of mental being.