Token-identity

There are two other notions in terms of which one may try to provide a criterion for sharing a domain explanation and token-identity. The idea that explanation can do the job comes from the philosophy of science, where it is often said that a new and better theory should explain the successes and failures of its predecessor. The superior theory is expected to make clear why the inferior theory worked in certain cases and why it failed in other cases. One may try to elevate this explanatory relation into a criterion for sharing a domain. So one may say that Aristotelian physics and mechanics intersect because we can account for the successes and failures of Aristotelian physics in terms of mechanics. This solution seems unsuitable for several reasons. One may note that it is theories which explain, not... 

Again, this is not an objection to token-identity. Rather, it is something we should accept if choose token-identity. 

This suggests that what guarantees translatability in the absence of a close match between predicates is agreement about individuation. However, I said that conceptual schemes may differ about individuation as well. If we have neither type-reducibility, nor token-identity, translation may be impossible. So it looks that what I said about conceptual schemes still involves an untranslatability claim. I am not sure I would like to commit myself to this, but suppose I do. In this case I have to show that this commitment can be maintained. To be precise, what I have to show is this. There may be discourses having a common subject matter - or domain, to use the term from (IR3) - which both classify and individuate differently. 

So on this view, although mental properties are distinct from and irreducible to physical properties, every mental event is token identical with some physical event. Thus, for example, the mental event of my being in pain might be token identical with the physical event of enhanced substance P production. So there would be, for instance, a single event E, which causes my behavior of sa)dng ouch . This event E has both physical properties (higher concentrations of substance P) and mental properties (painfulness). These mental properties supervene on the physical properties, but yet are irreducible to the physical. 

At the very least, M and P must be related by supervenience. However, it may be that mere supervenience is not enough to give us an adequate accoimt of mental causation within a physicalist framework. We might want to hold a view like Davidson s, where not only does M supervene on P, but P realizes M, and M and P are properties of a single event. So as properties, M and P are distinct, but as event, M and P are token identical. Whether physicalism requires mere supervenience, a picture like Davidson s with realization and event identity, a functional reduction of M to P as Kim advocates, or a fullblown type identity of M and P will be discussed shortly. 

Now how does all of this pose a problem for nonreductive materialism Nonreductive materialism holds that although every mental property supervenes on some physical property (and is possibly also realized by tiiat physical property and token identical with it as event), mental properties are neither type identical with nor reducible to physicjd properties. Now in order to give an adequate account of mental causation, the nonreductive materialist will need to be able to say how it is that mental events can be causally potent - i.e., how can a mental event M cause another mental event M to occur, and how can a mental event M cause a physical event P to occur Now if we are working with a Davidsonian model and we have token identity, where every mental event is token identical with its physical instantiation base, then there is no problem with event causation. Mental events are causal because theyjust are physical events. But the... 

This version of the exclusion principle seems quite plausible, with not much argument needed to convince us of its truth. It seems right to say that two distinct events cannot both be causes of e, if one of the events is a sufficient cause of e (and it is not a case of overdetermination). But notice that Kim here speaks in terms of events rather than properties. It is not clear why Kim does this here, since on a Davidsonian model of nonreductive materialism, the mental and physical events would be token identical and would not be two distinct events. What we would have is a single event with distinct mental and physical properties. 

Thus, if we use this version of the exclusion principle in Kim s exclusion argument, we will not get Kim s desired conclusion. This version of the exclusion principle says that two distinct events cannot both cause P. But as long as we hold the event identity of M and P, then as event, M and P are token identical. M and P are only distinct as properties. Since this version of the exclusion principle only requires us to rule out distinct events as both being causal, but not distinct properties, this version will not force us to rule out either M or P as a cause of P. Thus, this version of the exclusion principle, while independently plausible, will not get Kim to his desired conclusion (8) -i.e. that mental property M gets excluded by physical property P as the cause of P. ... 

The above considerations show that as long as we hold M and P to be token identical events, Kim s plausible version of the exclusion principle will not rule out mental events as causal. This is good reason for the nonreductive materialist to hold a Davidsonian view of event identity. It seems that a mere supervenience or realization relation between M and P is not quite enough. In addition to supervenience and realization, it seems that we also need the token event identity of M and P, in order to avoid M getting ruled out as causal by the plausible exclusion principle. Thus, fijom this point forward, I will assume that any viable nonreductivist position requires that M and P are token identical events. I will, from now on, assume a Davidsonian event identity. 3.3 Kim s second formulation of the exclusion principle Kim s second formulation of the exclusion principle, which actually appears in the exclusion argument is as follows ... 

Note this only means that this instance of M this instance of P. Does this mean that a Davidsonian token identity suffices here The answer is no the relevant sense in which an instance of M = an instance of P requires either property identity M = P or some form of reductive relationship between them.... The fact that properties M and P must be implicated in the identity, or nonidentity, of M and P instances can be seen fi-om the fact that An M-instance causes a P-instance must be understood with the proviso in virtue of the former being an instance of M and the latter an instance of P. (Kim 2005 42, footnote 9). 

Ron McClamrock (1995a, ch. 3) has argued that we can use the ideas of multiple realizability and context dependence to pick out preferred levels of causation and explanation. When we have token identity at different levels, we can use the ideas of multiple realizability and context dependence to hold properties at one level fixed while varying properties at other levels, in order to try to see at which level the causal mechanism occurs. In the ball-sorter case, we see that the causation occurs in virtue of size and that the macro-level of size is the right level of explanation. 

The next two chapters apply the core notion and a few derivative notions to reduction debates in the philosophy of mind (Chap. 6) and the philosophy of science (Chap. 7). Type-identity theories, token-identity theories, conceptions of non-reductive physicalism, and the model of functional reduction can easily be reconstructed based on the explication proposed here, sometimes in an improved form (for example, on the view presented here, it becomes immediately clear where the directionality stems from - an aspect that has been ignored in the heat of the... 

Now it is time to show the relevance of the notion and the fruitfulness of the explication. The concept of reduction defined in the previous chapter is key to an understanding of the reduction-debate in the philosophy of mind. Reductive identity-theories, type-identity theories as well as token-identity theories, and models of functional reduction conceive of reduction precisely as described above These theories are supposed to reconcile strong unity with diversity and directionality according to this conception, a reduces to b only ifa = b. 

Now, type identity theories have been extensively criticized. Physicalists opposed to type-identity theory usually conceive of themselves as non-reducHve physicalists. Interestingly, understanding what non-reductive physicalism consists in requires us to understand what this doctrine is opposed to - namely, reductionism about (mental) types. Moreover, non-reductive physicalists often describe themselves as token-identity theorists, they assume that mental tokens reduce to physical tokens, so that there is strong unity at the token-level. Again, a notion of identity-based reduction is required to hilly understand this idea. The explication offered here cannot only be fruitfully applied in the context of type identity theory. The next section is dedicated to the connection between the explication of reduction and token identity theories. 

This book is not about reductionism and, accordingly, not about the question of whether or not arguments from multiple realizability affect the truth of type-identity theory. However, this book assumes that the concept of reduction is relevant. If the argument from multiple realizability goes through, and if token-identity theories are in some sense non-reductive, then one might wonder whether the concept of reduction is relevant. Let me thus show that token-identity theories employ a notion of reduction similar to the one employed by type-identity theories - a notion that can, again, be defined based on the explication offered above. 

Intuitively, token-identity theory can be described in analogy to type-identity theory For any token of any mental kind, it is identical to a physical token. Note firstly that this version of token-identity theory follows from type-identity theory... 

So, how does token-identity theory connect to the notion of reduction Even though it is not a very common term in the literature, we sometimes find variants of the expression token reduction (Cartwright 1999, 32 ff., Hooker 1981, part III Bickle 1998, 223 ff.). Consider the following claim to get an idea of how token-identity theory (as intuitively sketched) relates to our paradigm case of reduction ... 

Token-identity theorists (concerning folk-chemistry) may deny this claim and suggest a different reading ... 

Does an explication along these lines, plus a denial of type-identity theory, capture the intuition behind token-identity theory Token identity theorists assume that H2O is more fundamental than water. Even if, on their view, the kind water does not reduce to the kind H2O, there is directionality involved being a water-token is less fundamental than being an H20-token. Similarly, if substance dualism is false then thoughts reduce to brain-processes, what appears to you as the referent of T , when uttered by you, reduces to the spatio-temporal, physical object or chain of events that is you, and your particular mind reduces to the set of particular neural and, maybe, bodily events, just like every other mind reduces to the corresponding neural and bodily substance or chain of events. Thus construed. 

Just as an aside Nominalists should be cautious when embracing token physicaUsm as opposed to type-identity theory. Under a nominalist conception of absiracta, it may, depending on how modal operators enter the formulation of token identity theory, imply type-identity theory for co-extensional properties. 

The notions of type- and token-reduction introduced here bear upon an appropriate understanding of anti-reductionist aspirations in the context of ontological non-reductive physicalism If we assume that there are different, irreducible kinds of properties, but still assume that token- or substance monism is true, then we could use the notion of token-reduction and type-reduction to capture this idea. Non-reductive physicalism, in its ontological version, consists in the affirmation of token-reduction and the denial of type-reduction for the relevant class of tokens and types. The explication proposed above enables us to give an idea of what reductive type- and token-identity theories consist in, and, combing the two, it yields a characterization of non-reductive physicalism. The next sections discuss the application of the explication of reduction to more recent versions of type-identity theory. 

The explication proposed in the first part of this book sheds light on conceptions in the philosophy of mind, such as various conceptions of type identity theory, token identity theory and non-reductive physicalism. We thereby motivated the explication - it is not only adequate, but also fruitfiil. 

The two most prominent ontological positions in the philosophy of mind, type-identity theory and token-identity theory, build upon an understanding of reduction that is captured by the job-description that reduction is supposed to reconcile diversity and directionality with strong unity. These theories differ in their interpretation of where to look for unity - on the level of types or on the level of tokens. As such, they do not differ in other respects. Both sorts of theories are underdetermined with respect to directionality and diversity. The explication proposed above fixes these deficiencies. Moreover, it neatly matches the commitments concerning the... 

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