Analysis of Matter

Analysis of Matter

What is the general nature of concepts of matter? How are such concepts to be analyzed? Is there a general nature or only a plurality of concept-types? Ryle wrote a book called The Concept of Mind (note the uniqueness implied by “the”), arguing that mental concepts are generally dispositional in form; what would a book called The Concept of Matter contain? I will begin to answer this question by considering the concept of motion (someone could write a book with this title too), a concept vital to physics. So I am concerned with the analysis of matter-in-motion: how do we conceive of matter-in-motion, and how should we conceive of it? What is the “logical structure” of this concept? This question is not to be distinguished from the question of what motion is—or what it is for a material object to move. What is the logical form (conceptual analysis) of, say, “The earth moves”?

            Immediately we are confronted by a difficulty, because there is controversy about the nature of motion. Some say it is absolute and some say it is relative (I say it is both, but we will get to that). We don’t need to settle the question for present purposes, since we can consider my question under either assumption. So suppose it is relative: motion only makes sense against the background of a plurality of objects, consisting in relative change of position. Then we can say that motion statements are relational in form: roughly, “the earth moves” means “the earth changes position relative to some object x”. The object in question may be indefinitely distant from the object said to move, so motion is not a local property of an object (the motion of the earth is usually referred to the sun). This is not apparent on the face of the statement we are analyzing, but that is not generally any objection to an analysis. We say, then, that the predicate “x moves” means “x moves relative to y”. I shall say that the concept of motion is an object-introducing concept, meaning that it refers us to an object not initially supposed essential: it is as if we can’t speak of x moving unless we are first introduced to another object y. We can’t speak of motion in isolation but only in the context of a system of objects. Motion is essentially relational. To put it differently: motion is not locally supervenient; it depends on what is going on in the environment of the object in question. It is not internal to the object that is said to move. It is not an individualistic property. We need to be externalists about motion, recognizing that motion only occurs in a certain context—it is object-dependent or object-involving. The moving object is only so in virtue of being embedded in world in which other objects exist that confer motion on it. The state of motion of one object incorporates the state of motion of other objects.

            I have put the point in these ways because I want to explore an analogy between motion and mental content. According to a dominant tradition, motion was conceived as an inherent property of an object, intrinsic and internal. An object could be in motion even though no other object existed. But a counter-movement arose that questioned this idea: motion is something that essentially involves other objects, even remote ones. Similarly, there was a tradition that located mental content within the subject, so that what you mean or think is independent of anything in your environment: it is a matter of your brain or your inner subjective state. But a counter-movement arose that questioned this idea: content is something that essentially involves other objects, even remote ones. Thus we are treated to twin earth cases and other ways of demonstrating the object-dependence of mental content. The environment fixes content—as it fixes motion. Externalism about meaning and motion became received wisdom. And these doctrines were intended to capture the actual character of our concepts, which had previously been misunderstood. As the slogan goes, “meanings are not in the head”; and neither is motion “in the object”—it’s in the relation between objects. In my terms, the concepts of meaning and motion are object-introducing concepts. That is their logical structure—what they logically imply. Thus all the characterizations that are applied to the mind can be carried over to matter-in-motion: externalism, anti-individualism, non-locality, non-supervenience, relationalism, environmental determination, object-dependence, etc. We thought that motion was internal to objects, part of their inner nature; but now we see that motion lies in the connection between one object and another, a matter of their external relations. The concept of motion is therefore a concept with an internal complexity that extends beyond its initial appearance—dyadic not monadic, two-factor not one-factor. Note, particularly, that it characterizes a fact that extends across space to possibly remote objects, and indeed brings in every object in the universe. It is not just a property of an isolated object doing its thing locally, sublimely unconcerned about everything else. It isn’t like shape or mass or atomic structure. It is more like size or length or being up or down: things have these attributes only relative to other things not intrinsically.

            One might think that the relational analysis only works if we accept relative motion not absolute motion. But that is not quite right, because so-called absolute motion is not really absolute: it is motion relative to space, conceived as eternally static and at rest. As Newton understood it, the motion of a body occurs against the background of an unmoving spatial manifold: space stays where it is while objects pass through it. So all motion is relative to something, though not to other material bodies. This something, however, is highly local, being either contiguous with the moving body or pervading its volume. So motion is relative but local on this conception: moving through an enveloping space. And what it is relative to is of a different nature from the moving body itself—space not being a kind of matter. So the concept of motion relates the moving object to a surrounding entity—viz. space—relative to which it moves; it is still a relational entity-introducing concept (I say “entity” not “object” because space is not a material object in the style of the relative theory of motion). Logically, then, the two views are not that far apart, despite the difference of ontology. A truly internalist view of motion would suppose that motion is entirely intrinsic to the object, not even relative to space. Thus this kind of absolutist would insist that even if the surrounding space did not move relative to the object the object might still be moving: for both the object and surrounding space might both be moving! Only if we suppose space to be necessarily at rest can this possibility be ruled out, but even then the following counterfactual might be true: “If space were to move along with an object, that object would still be moving”. That is, the concept of motion allows for the conceivability of motion without change of relative position with respect to space. This makes motion super-intrinsic—independent even of space (as presumably shape is: things are not triangular relative to their surrounding space).

            Here our analogy proves helpful. Consider a super-internalist who holds not merely that mental content is independent of the environment but also is independent of the subject’s brain and inner subjective state. This internalist holds that content is completely intrinsic to concepts themselves and is not dependent on anything outside of it—not the brain and not the subject’s subjective experiences. He might maintain that the mind is not the brain but an immaterial substance, and that we could vary a person’s subjective state and keep his concepts constant. For example, we could vary his senses and their phenomenology while not changing what he thinks and means: his concepts are not supervenient on his brain states or sensory states. They are supervenient on nothing but themselves (and possibly the immaterial substance). The usual kind of internalism supposes that the independence concerns only the external environment, but this extreme kind of internalism takes concepts to be independent even of states internal to the subject (not including concepts themselves). Thus we have externalism, internalism, and super-internalism (“intrinsicalism”); and similarly we have three views of motion—relativity to remote objects, relativity to space, and relativity to nothing save itself. That last view may not be plausible—it may not even be coherent—but it exists as an option that someone might adopt. After all, geometric properties are not defined relative to space: a circle is not circular only in relation to non-circular space, whatever that may mean. In any case, the two leading contenders for the nature of motion both regard it as fundamentally relational—much as mental content is regarded as fundamentally relational. Reflection in both cases has persuaded us that a superficially monadic concept is really a dyadic one. In the case of the relative theory of motion the extra object can be remote from the given object, while in the case of the absolute theory (so-called) it is as proximate as could be. The absolute theory should not be saddled with the idea of completely non-relative motion, which makes dubious sense; instead it is a question of which entity motion is relative to and where that entity is located. The absolutist might say, “Of course motion is relative, only not to remote objects but to surrounding space!”

            But which theory is true? I will not attempt to adjudicate that question; I will merely note that both could be. That there is such a thing as change of relative position there can be no doubt, and if we choose to call that motion (not unreasonably), then relative motion exists. But it doesn’t follow that no other kind of motion exists: maybe there is absolute motion as well. Objects could move relative to each other and relative to space. If I say to you, “Don’t move till I get back!” I don’t intend to blame you for your motion as the earth moves; I mean relative to the room you are in. But I can also talk about motion with respect to space and mean precisely that (rightly or wrongly—rightly in my view). Thus we have two concepts of motion that coexist in our conceptual scheme, and hence two types of conceptual analysis.  [1] They vary in their ontology but they are similar in logical form. Accordingly, we recognize two types of property when we use motion words, so we conceive of matter in two different ways: bits of matter change relative positions, but they also change their relation to space—they are capable of doing both. It follows that our concepts of motion have different analyses. This is analogous to the claim that we have two concepts of content, wide content and narrow content, which can coexist. Both are legitimate and useful, though they are differently defined and serve different purposes.

            Do all concepts of matter fit this pattern? I have already suggested that concepts of shape or configuration don’t: here there is no submerged relationality, whether remote or proximal–internalism rules. Geometric concepts are not covertly object-introducing; they are self-enclosed and just as they appear. I think the same thing is true of the concepts of mass and charge: these are not defined relative to some environmental variable—we would not be right to be externalists about these properties. They look like dispositional concepts, and as such refer to interactions with other things; but the same thing is true of all dispositional concepts, mental or physical. No one is surprised by this kind of relationality; by contrast, it comes as something of a revelation to discover that motion is relative (it is somewhat similar with size and length). Motion is a bit like color in this respect: we start off thinking color is intrinsic to objects and then are surprised to find that it depends on relations to perceivers. Whether a given object is red depends on whether other distant objects (i.e. perceivers) see it as red; color isn’t written into the object considered in itself. So it seems that we have three types of physical concept in our repertoire: intrinsic (shape), dispositional (mass and charge), and object-introducing (motion and size). There is not a single homogeneous type; physics is made up of three distinct concept-types with three different kinds of analysis. It would be pleasant to report that psychology is likewise made up of three such types, and arguably it is  [2]; in any case, conceptual heterogeneity holds in the case of the science of matter. This is a result in the conceptual science of science.

Colin McGinn

  [1] Imagine a possible world stipulated to contain both sorts of motion: it contains an absolute space with respect to which objects move, as well as the more humdrum kind of relative motion. Then inhabitants of that world would need two concepts to cover the facts. It seems to me that in our world we have two sorts of concern to which talk of motion answers—practical and theoretical, to put it briefly—so we naturally employ two concepts. The case is somewhat like the concepts of weight and mass. Put tendentiously, one kind of motion might be designated realand the other apparent.

  [2] There are mental states with content like beliefs and desires, which are object-introducing; there are mental traits like irascibility and generosity, which are dispositional; and there are occurrences like being in pain or feeling moody that are non-relational and non-dispositional.