Abstract
Leibniz’s World-Apart Doctrine states that every created substance is independent of everything except God. Commentators have connected the independence of substance asserted by World-Apart to a variety of important aspects of Leibniz’s modal metaphysics, including his theory of compossibility and his notion of a possible world (including what possible worlds there are). But what sort of independence is at stake in World-Apart? I argue that there is not a single sense of “independence” at stake, but at least three: what I call “causal”, “phenomenal,” and “ontological” independence. Further, I distinguish two versions of each type of independence: what I call “basic” and “strict” versions. I argue that only basic versions can be legitimately attributed to Leibniz. In light of this result, I conclude, pace previous commentators, that World-Apart has little impact on Leibniz’s modal metaphysics.
I would like to thank Marleen Rozemond, Kristin Primus, Laura Herrera Castillo, and the participants of the Early Modern Circle for helpful comments on earlier versions of this paper.
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Notes
- 1.
This label is courtesy of Sleigh (1990), 180.
- 2.
- 3.
The question whether Leibniz was committed to World-Apart prior to 1686 will be left aside for now. Note, however, that the phrase “monde à part” occurs as early as 1679. See A.VI.iv.2235, 2270.
- 4.
Thanks to Kristin Primus for suggesting the term “Causal Independence, Phenomenal Independence and Ontological Independence”.
- 5.
There is some controversy surrounding just what is contained in the complete concept of a substance and what is deducible from the complete concept, some commentators argue that deducible from can also rely on independently specifiable features of the world, such as the laws of nature. For discussion, see Sleigh (1990), 72 ff. The basic type of independence articulated by the complete-concept characterization might be called “semantic independence.” I will not develop this notion directly, since I think of it as a weaker form of phenomenal independence.
- 6.
Expression is a very general notion for Leibniz. See, e.g., A.II.ii.240/LA.144: “One thing expresses another (in my terminology) when there exists a constant and fixed relationship between what can be said of one and of the other.”
- 7.
See also A.II.ii.81/LA.51.
- 8.
As I will discuss below, it is not clear whether substances that do not conform to each other can be properly characterized as occupying the same world. See, e.g., the following text: “God could have given each substance its own phenomena, independent of all others; but in so doing he would have made as many unconnected worlds, so to speak, as there are substances […] (Histoire des ouvrages des savants, July 1698, 333/WF.81). I will consider this remark (as well as other remarks from the same text) further below. There is some textual basis for thinking that Leibniz explicitly allows for God to create multiple different worlds along these lines. See, e.g., A.VI.iii.511–512/DSR.65-7. For discussion, see Griffin (2013), 104.
- 9.
There is controversy about whether so-called relational predicates can really be included in the concepts of substances. For arguments against, see, e.g., Cover and O’Leary-Hawthorne (1999), 96 and 132. For arguments in favor, see, e.g., Chiek (chapter “Compossibility and Co-possibility” in this volume). The example is purely for the purpose of illustration and is not meant to commit to one side or the other of this question.
- 10.
This has interesting connections with things Leibniz says elsewhere concerning the reality of phenomena, matter and motion in particular. See, e.g. GP.VII.320/L.364; GP.II.270/L.537. I will discuss this to some extent below.
- 11.
Despite the phenomenal independence asserted by World-Apart, Leibniz is clear that, on his view, there is good reason to think that other substances do exist, answering to our representations of them. DM §14 continues: “Nevertheless, it is very true that the perceptions or expressions of all substances mutually correspond in such a way that each one, carefully following certain reasons or laws it has observed, coincides with others doing the same […]” (A.VI.iv.1550/AG.47). This remark opens questions concerning the modal status of the existence of members of the actual world and will be left aside until the next section.
- 12.
As we will see when we turn to the letters to Des Bosses, Leibniz will later claim that reasonable judgments made on the basis of true phenomena will not be erroneous even if nothing external exists.
- 13.
Leibniz sometimes contrasts “true phenomena” with substances. See, e.g., the following passage from “Primary Truths”: “Extension and motion, as well as bodies themselves (insofar as only motion and extension are placed in bodies) are not substances, but true phenomena [phaenomena vera], like rainbows and parhelia” (A.VI.iv.1648/AG.34). This use of “true phenomena” is connected to Leibniz’s notion of well-founded phenomena; it is ultimately an expression of the reality of phenomena, even though Leibniz uses the term “vera” here.
- 14.
I will return to this question when I consider Leibniz’s correspondence with Des Bosses in Sect. 4.
- 15.
“Thus by no argument can it be demonstrated absolutely that bodies exist, nor is there anything to prevent certain well-ordered dreams from being the objects of our mind, which we judge to be true and which, because of their accord with each other, are equivalent to truth so far as practice is concerned” (A.VI.iv, 1502/L.364).
- 16.
I use “universal perception” to signial a difference between this commitment and Leibniz’s view that each substance expresses the entire world. Expression proper would incorporate both universal perception and universal accommodation. This issue is, however, a bit complicated and cannot be spelled out fully here. Thanks to Laura Herrera Castillo for discussion of this point.
- 17.
For development of a similar distinction, see Sleigh (1990), 176 ff.
- 18.
- 19.
Universal accommodation could be made consistent with ontological independence, if formulated as follows: every (created) substance accommodates, agrees with, or harmonizes with all other existing substances. Given this formulation, a substance need not accommodate a specific collection of other substances, but could simply accommodate whatever other substances happen to exist; thus, it would not require the existence of any specific others. But this would depart from Leibniz’s view.
- 20.
For Bayle’s criticism, see note H to the article “Rorarius” in Bayle’s Dictionaire Historique et Critique i. 966–7/WF.72–5).
- 21.
The passage from the New System continues to characterize the World-Apart Scenario as a “manner of speaking” (GP.IV.484/AG.143).
- 22.
See, e.g., the following passage from “Infinite Numbers” (1676): “But to say all numbers is to say nothing” (A.VI.iv.502/RA.99).
- 23.
For Leibniz’s treatment of infinite series, see, e.g., A.VI.iv.503/RA.99.
- 24.
For further discussion of the role of mental fictions in the case of infinite number, see Harmer (2014), 250 ff.
- 25.
I will consider below the connection between Leibniz’s use of “metaphysical possibility” here and his familiar distinction between absolute and hypothetical necessity.
- 26.
This has been designated as the “Principle of Intelligibility.” For further discussion, see Rutherford (1992). Rutherford characterizes the “Principle of Intelligibility” as the commitment that everything that happens can be given a natural explanation. For examples of this in Leibniz, see, e.g., the following text from the same reply to Bayle regarding miracles: “It isn’t sufficient to say that God has made a general law, for in addition to the decree there has also to be a natural way of carrying it out. It is necessary, that is, that what happens should be explicable in terms of the God-given nature of things” (Histoire des Ouvrages des Savants, July 1698, 336/WF.82). See also the following text from the Preface to the New Essays, where Leibniz claims that thinking matter would be unintelligible given the nature of matter: “Whenever we find some quality in a subject, we ought to believe that if we understood the nature of both the subject and the quality we would conceive how the quality could arise from it. So within the order of nature (miracles apart) it is not at God’s arbitrary discretion to attach this or that quality haphazardly to substances. He will never give them any which are not natural to them, that is, which cannot arise from their nature as explicable modifications” (A.VI.vi.65/RB.65).
- 27.
Leibniz’s remarks might be construed as asserting that the existence of other substances impedes the actions of each one. It is worth highlighting, though perhaps obvious, that this remark is compatible with the causal isolation of substance, since a substance’s actions—whether or not they are impeded—flow from the determinate nature of the substance in question. Thus, the impediments are built into that nature and only originate in another substance ideally. For Leibniz’s discussion of ideal influence see, e.g., A.VI.vi,.210/RB 210.
- 28.
Leibniz’s reliance on this distinction is pervasive. For a standard formulation, see, e.g., DM §13 (A.VI.iv.1546–7). Leibniz also presents a theory of contingency in terms of infinite analysis. I will not discuss this view here, but see, e.g., “On Freedom” (A.VI.iv.1653/AG.94).
- 29.
See, e.g., the post script to Leibniz’s fourth letter to Samuel Clarke, where Leibniz applies this consideration to argue against empty space and in favor of the actual subdivision of matter to infinity (GP.VII. 377–8).
- 30.
By “truth of judgments” here, I simply mean judgments not made in error.
- 31.
- 32.
I will not even be able to present the competing options fully. Broadly, there are three approaches to compossibility in the literature. The logical interpretation (e.g. Mates 1972; Rescher 1979), the lawful interpretation (e.g. Russell 1937; Cover and O’Leary-Hawthorne 1999), and the cosmological interpretation (e.g. Messina and Rutherford 2009).
- 33.
See also, e.g., GP.III.573/L.662: “[…] not all possibles are compossible. Thus, the universe is only a certain collection of compossibles, and the actual universe is the collection of all existing possibles, that is to say, those which form the richest composite. And since there are different combinations of possibilities, some of them better than others, there are many possible universes, each collection of compossibles making up one of them.”
- 34.
For commentators who offer a logical interpretation of the compossibility relation, see, e.g., Hintikkaa (1972), Mates (1972), Rescher (1979), D’Agnostino (1976), and Chiek (chapter “Compossibility and Co-possibility” in this volume). For those who reject the logical interpretation on the basis (at least in part) of World-Apart, see, e.g., Messina and Rutherford (2009), 963–5 and Cover and O’Leary-Hawthorne (1999), 136. While Messina and Rutherford make this point directly, Cover and O’Leary-Hawthorne make it indirectly. (They argue against maximality—each possible world contains all substances compossible with its members—directly on the basis of World-Apart and use this to argue against the logical interpretation.) Cover and O’Leary-Hawthorne argue directly against the logical approach on the grounds that no two substantial concepts can contradict one another because they (the concepts) do not contain relational predicates. See Cover and O’Leary Hawthorne (1999), 132 and 138.
- 35.
- 36.
See, e.g., Mates (1972), 341 and Rescher (1979), 17. Although excluding all incompatible possibles follows from the logical interpretation of compossibility directly, requiring all compatible possibles does not. Typically, the latter is thought to follow from the logical interpretation combined with a certain understanding of universal expression (each substance expresses all compossible substances) and maximality (each possible world contains all substances compossible with its members). This will be discussed below.
- 37.
McDonough highlights it as a traditional feature of substances that they are entia in se and per se (McDonough 2010, 137). He takes this to mean that “no substance per se entails the existence or nonexistence of any other substance” (ibid., 136). I agree that entailing the existence of another would undermine independence; it is not at all clear to me, however, that entailing the nonexistence of another would do so. I will return to this point below.
- 38.
For discussion, see Mates (1972), 340–1 and Rescher (1979), 49–50. For discussion (and criticism), see Messina and Rutherford (2009), 964. Mates relies on Theodicy 212, while Rescher argues for maximality on the basis of conceptual interconnections between the complete concepts of substances. Messina and Rutherford criticize the commitment to maximality on the grounds that it violates the World-Apart Scenario and that it constrains God’s power to create.
- 39.
There may be other reasons to argue that Logical Compossibility needs maximality, perhaps to address certain problems or objections.
- 40.
Commentators often distinguish between intrinsic and extrinsic compossibility. Intrinsic compossibility: substances are compossible per se. Extrinsic compossibility: substances are compossible in virtue of certain choices God makes, for example, the selection of certain natural laws. Commentators also frequently claim that World-Apart entails the intrinsic compossibility of any substances whatsoever. See, e.g., Cover and O’Leary-Hawthorne (1999), 137 and McDonough (2010), 137–8.
- 41.
Thanks to Marleen Rozemond for helping me to clarify this point.
- 42.
A different way to articulate this limited restriction on the ontological independence of substance would be as follows: perhaps the strict ontological independence of substance only applies to sets of compossible substances. That is, within any set of compossibles, the existence of one neither requires nor excludes the existence of any other substances. But this claim cannot be made unrestrictedly about all substances. This also highlights the fact (in my view) that the precise claims made by World-Apart depend on our answers to other, more basic modal questions.
- 43.
For development of the view that World-Apart entails a rejection of maximality, see Cover and O’Leary-Hawthorne (2009), 136.
- 44.
There is some reason to question whether a single substance could constitute a possible world even if God could choose to create only a single substance. For discussion of the distinction between “possible creations” and “possible worlds” see Griffin (2013), 87 and 103.
- 45.
See, e.g., Theodicy §225: “The wisdom of God […] goes even beyond the finite combinations, it makes of them an infinity of infinites, that is to say, an infinity of possible sequences of the universe, each of which contains an infinity of creatures” (GP.VI.252/H.267). As Sleigh (1990), 180 notes, this passage does not strictly entail that all possible worlds contain an infinity of creatures, just that infinitely many of them do. I am inclined to interpret this passage more loosely than Sleigh does and take it as some (if not conclusive) evidence in favor of maximality.
- 46.
Sleigh rightly notes that admitting sub-maximal possible worlds gives rise to the problem that the very same substance could be in more than one possible world. For example, I am in the actual world and I would also be in the world containing only me. This threatens to create tension with Leibniz’s denial of transworld identity. However, as Sleigh also notes, this problem is dulled by the fact that one of the two worlds in which the same substance exists is a proper part of the other. For discussion, see Sleigh (1990), 182
- 47.
Sleigh (1990), 181, Cover and O’Leary-Hawthorne (1999); 136, and Messina and Rutherford (2009), 973. Messina and Rutherford’s view is subtle: they argue that anything God chooses to create as a world will be maximal. God could create a less-than-maximal collection of substances, though it would not constitute a world.
- 48.
In the Discourse, Leibniz holds that substances express all possibles not merely all compossibles (see DM §29/A VI.iv.1574). For discussion, see Sleigh (1990), 173. If this extends to the perceptions a substance has, it would be difficult to argue that the conception of an individual contains all and only its world-mates – but I see no reason to extend the claim in this way. Mates and Rescher argue that substances express all and only the substances in their world. They argue further that in virtue of expressing all compossibles, all compossibles must exist. I see no need to draw this final conclusion. In my view, it is true that a substance must perceive an entire world, but it does not follow that the world must exist, not, at any rate, if the “must” here is understood as a logical or metaphysical necessity. See also footnote 36.
- 49.
Commentators have argued that in light of the fact that the concepts of substances contain only simple properties, there is no way to build relational information (e.g. information about other substances) into the concepts of substances. See, e.g., Mates (1972), 351–2 and Cover and O’Leary-Hawthorne (1999), 132. Others have argued that relational properties should be included in the complete concepts of substances. See, e.g., Rescher (1979), 55. Along these lines, it would be nice to be able to answer the following question: could a single substance exist and represent only itself? Or, further is there a possible world with only a single substance in which that substance both perceives and accommodates that world? There is a lack of textual evidence available to address this question; however, my (admittedly speculative) inclination is to say no to both questions. Unfortunately, I cannot develop this any further here.
- 50.
Some commentators defend the conceptual priority of the notion of a world to the notion of compossibility. See, e.g., Messina and Rutherford (2009), 969 and Wilson (2001), 10. For discussion, see Griffin (2013), 102 ff. Messina and Rutherford, moreover, provide an account of what it means to be a “general system of phenomena”: in their view, it is to be part of a spatiotemporal order.
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Harmer, A. (2016). Leibniz’s World-Apart Doctrine. In: Brown, G., Chiek, Y. (eds) Leibniz on Compossibility and Possible Worlds. The New Synthese Historical Library, vol 75. Springer, Cham. https://doi.org/10.1007/978-3-319-42695-2_3
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