The idea here is that because substances are independent subjects, the annihilation of one subject cannot have any consequence for the others. The problem with this is that the hole in the cheese is measurable—it has a diameter, a circumference, etc. In short, it is extended.
However, we have supposed that the extended substance—the subject of the extension—in the middle was destroyed. For detailed discussions of this argument see Huenemann and Robinson In fact, Leibniz corresponded with Spinoza during the early s and briefly visited with Spinoza in Unlike Spinoza, Leibniz did not write a single authoritative account of his metaphysical system.
Not only that, but his metaphysical views changed in significant ways over his lifetime. 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 of through the Monadology of Second, Leibniz explicitly agrees with Descartes, Spinoza, and the tradition in maintaining that substances are the ultimate bearers of modes or properties. 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.
They can neither begin nor end naturally, and consequently they last as long as the universe. Thus only composite entities are naturally generable or destructible. 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. Substances, in some sense, have their entire history written into their very nature. The history of each substance unfolds successively, each state causally following from the previous state according to laws.
Like Spinoza, Leibniz holds both that substances are causally efficacious, and that their efficacy does not extend to other substances. In other words, although there is intra-substantial causation insofar as substances cause their own states , there is no inter-substantial causation. Leibniz offers a number of different arguments for this claim. On some occasions he argues that causal isolation follows from the nature of substance.
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. 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.
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For Descartes there are fundamentally two kinds of finite substance—thinking substances or minds and extended substances or bodies. Leibniz disagrees; according to Leibniz and this is especially clear in the later works there are no extended substances. Nothing extended can be a substance since nothing that is extended is a unity.
To be extended is to be actually divided into parts, according to Leibniz, and consequently to be an aggregate. Rather, there is a whole spectrum of simple substances of which human minds are a particularly sophisticated example. God exists and is responsible for creating and continually conserving everything else. The ultimate constituents of reality are monads which are indivisible and unextended minds or mind-like substances. This article will take up three in particular. 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.
How, then, is the world of our experience related to the world as it really is? Let us begin with the apparent causal relations between things. Recall that, for Leibniz, monads are active and spontaneous. Leibniz writes in A New System of Nature ,. God originally created the soul and any other real unity in such a way that everything must arise for it from its own depths…yet 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.
How does our experience of an extended world of bodies arise? He writes in an oft-cited passage to DeVolder:. 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. 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 being extended.
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 b: Leibniz thinks composite beings are excluded as possible substances on a number of grounds. First, 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. He famously illustrates this claim by appealing to two diamonds. He writes in his Letters to Arnauld :.
One could impose the same collective name for the two…although they are far part from one another; but one would not say that these two diamonds constitute a substance…Even if they were brought nearer together and made to touch, they would not be substantially united to any greater extent… contact, common motion, and participation in a common plan have no effect on substantial unity. In general, there is no relation that two or more entities might be brought into that would unify them into a single being. A second and perhaps even deeper problem with composites is that according to Leibniz they cannot be ultimate subjects.
For example, what constitutes the essence of an army is only a mode of the men who compose it. This leaves us with a question, however: Why does Leibniz think that aggregates are mere modes or states of their parts? In his influential book R. 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. 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.
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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 He would be right if there were no monads. 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. God is a substance and He produces finite substances—created monads. This signals a break from Spinoza in at least two significant ways.
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God does not produce effects in a metaphysically intolerable way, and consequently, God need not be causally isolated. Second, Leibniz holds, in contrast to Spinoza, that created substances are ultimate subjects. Leibniz is very explicit about his objection to Spinoza on this score. Looking back, we might see Descartes, but especially Spinoza and Leibniz, as working through the metaphysical consequences of holding that substances are ultimate subjects.
Epistemological considerations led prominent late 17 th and 18 th century philosophers to abandon such questions, and to give substance a much more modest position in their metaphysical systems. John Locke, for example, holds that there are substances and that they are ultimate subjects, but is wary of drawing any further conclusions.
Humean skepticism about substance and about metaphysics more generally survives in one form or another to the present day. Of course not everyone agrees with this tradition, and the nature of substance has been a question that many contemporary philosophers have taken up—albeit from different starting points than Descartes, Spinoza, and Leibniz.
Furthermore, among contemporary philosophers there is nothing like the consensus that we find among the 17 th century philosophers regarding ontology, dependence, reality, and God. Thus, it is commonly held that there are categories of reality beyond substance and mode or property , perhaps most prominently events or processes.
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—they are merely bundles or collections of properties.
Furthermore, most contemporary philosophers deny that it makes sense to talk about degrees of reality: Things are either real or not. Last, and perhaps most obviously, contemporary philosophers no longer agree that God exists and is a substance.
For a contemporary effort to offer an account of substance that is in the spirit of 17 th century discussions, see Hoffman and Rosenkrantz Tad Robinson Email: trobinson muhlenberg. Are Embodied Human Beings Substances? How is Substance Independent? How Many Material Substances? An Extended and Indivisible Substance?
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