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The implications of multiple realization for scientific methodology have recently been hotly debated. For example, neuroscientists have discovered distinct realizations for what appears to be a single psychological property and some philosophers have recently maintained that in such cases scientists will always abandon commitment to the single, multiply realized psychological property in favour of two, or more, uniquely realized psychological properties. This chapter explores such methodological claims by building on the dimensioned theory of realization and a companion theory of multiple realization. Using concrete cases, this chapter shows that such an ‘eliminate-and-split’ methodology is not always the case in actual practice. Furthermore, this chapter also establishes that whether scientists postulate unique or multiple realizations is not determined by the neuroscience alone, but only in concert with the psychological theory under examination. Thus, in a sense this chapter articulates, in the splitting or non-splitting of properties, psychology enjoys a kind of autonomy from neuroscience.

The idea of multiple realization begins with a simple thought: There exists sameness of kind at one level of description, and differences in kind at a lower level of description. Two organisms, for instance, might be described as sharing a perceptual state, while differing in the physical states that realize this state. When investigating the possibility of multiply realized psychological states, one cannot confuse psychological similarity with behavioral similarity, as one might when investigating whether a capacity like face recognition might be multiply realized. Two kinds of organism might be able to recognize faces, but only one (or neither!) might do so through psychological means. The shared behavior is thus not evidence of a multiply realized psychological process. Finally, modal intuitions regarding the possibility of multiple realization do not come for free. They should be grounded in what our best sciences tell us about the prospects for actual multiple realization.

“Why There Are No Laws in the Special Sciences: Three Arguments” offers three arguments explaining why there are no laws, or “strict” laws, in the special sciences. The first of the arguments begins with a consideration of Donald Davidson's argument for his anomalism of the mental, the thesis that there are no laws about intentional mental phenomena. The second argument builds on some of J.J.C. Smart's observations concerning biology and its relationship to the fundamental science of physics. His claim is that, unlike physics, biology does not aim at the discovery of laws, and that engineering, not physics, is the correct model for understanding the status of biology. The argument yields a simple metaphysical argument for Davidson's anomalism of the mental. The last of the three arguments is based on the author's earlier work on multiply realizable properties and their projectibility. It argues that most special‐science properties are multiply realizable, and that multiply realizable properties, on account of their causal/nomological heterogeneity, are not inductively projectible and hence are not fit for laws.

This chapter compares role functionalism with other forms of color relationalism that have attracted philosophical adherents and argues that these alternative forms of relationalism all have serious drawbacks. Specifically, these forms include color dispositionalism, ecological relationalism, and sensory classificationalism. The author argues that dispositionalism either collapses onto role functionalism or rests on an implausible account of the relationship between dispositions and their bases. Ecological relationalism, on the other hand, falls prey to worries about multiple realization and is committed either to an unacceptable form of idealism or mislocates colors. Lastly, sensory classficationism links too tightly the perceptual classificatory responses of organisms and their subsequent epistemic or non-epistemic actions. With these contentions at hand, this chapter asserts that the role functionalism is the most promising species of relationalist color ontology.

Functionalism, or non-reductive physicalism, presupposes the possibility of multiple realization. Multiple realization, in turn, suggests an analysis of realization as an ontological dependence relation between entities that is distinct from other kinds of relations, such as identity, composition, or constitution. When seeking to discover whether a given entity is realized, one must ask a specific question: Is X realized by Y; similarly, questions about multiple realization will be contrastive: Is X realized by Y and Z? Within cognitive science, the questions of interest are whether psychological states are realized by brain states, and whether they are multiply realized by brain states as well as other kinds of states. Answers to these questions will depend on how the taxonomy of psychological states relates to the taxonomies of neuroscience as well, perhaps, as other sciences.

Block and Fodor classically offered three lines of indirect evidence for multiple realization: The Lashleyan doctrine of equipotentiality, evolutionary convergence on psychological traits, and the conceptual possibility of artificial intelligence. However, evidence of the first sort falls short of demonstrating that different kinds of brains can produce the same psychological functions by instantiating relevantly different neural properties. Evidence involving evolutionary convergence runs the risk of confusing convergence in behavior with convergence in psychological processing; and even if this difficulty is avoided, the presence of evolutionary constraints suggests that convergent psychological traits may well have convergent realizers as well. Finally, the conceptual possibility of artificial intelligence begs the question in favor of multiple realization. Given that no such intelligences exist today, no conclusions about the nature of their hypothetical realizers follow.

This chapter attempts to vindicate what is sometimes pilloried as the “Received View” of realization and multiple realization in the philosophy of mind. Using the Dimensioned view of realization, it proceeds to give three “mechanistic” accounts of how multiple realization is possible. There is what might be called multiple realization with individual variation, multiple realization by compensatory differences, and multiple realization by orthogonal realizers. It, then, shows how this multiple realization leads to a kind of autonomy of psychology, while nonetheless integrating neuroscience and psychology. It also shows how one might avoid “Keeley’s Dilemma” regarding the relationship between neuroscience and psychology.

Multiple realization requires sameness at one level of description and difference at another. But not any difference suffices for multiple realization. The differences should be relevant to the ways that the lower-level kinds bring about the function of the kind they realize. Differences in constitution thus may not suffice to distinguish between realizers of a kind. On the official recipe, multiple realization requires the existence of kinds that are the same according to one scientific taxonomy and different according to lower-level ones. Further, the differences at the lower level must account for the similarities that the kinds share at the higher level, and they must not account only for whatever intra-kind variation is present at the higher level.

Because the multiple realization thesis has been offered as an empirical hypothesis, attention must turn to the evidence on its behalf. Some evidence is direct, in the sense that it purports to reveal actual cases of multiple realization. Some is indirect, in the sense that it depends on establishing the truth of hypotheses compatible with multiple realization. This chapter examines direct evidence for multiple realizability, in the form of neural plasticity. The relevant sort of neural plasticity involves cases where damage to the brain results in new brain regions assuming the function of damaged regions, thereby purportedly exhibiting the multiple realization of a psychological state. However, close examination reveals that cases of neural plasticity do not obviously meet the criteria for multiple realization.

Of the various theories of mind philosophers have developed, the identity theory and functionalism have seemed the most promising. However, functionalism, because it allows for the multiple realization of psychological states, has been seen as superior to the identity theory. The simple idea is that a theory that denies multiple realization, as the identity theory does, cannot accommodate the possibility that different kinds of organisms share psychological states. Thus, functionalism enjoys a generality that the identity theory cannot match. But is the phenomenon of multiple realization that serves as the foundation for functionalism genuine? And is it true that the identity theory cannot generalize?

Critics contend that the categories within the DSM are fueling the current crisis in psychiatry because they are not valid. As a remedy, NIMH has established RDoC, a framework of psychological and behavioral constructs that will — they believe — better guide the search for the biological mechanisms of psychopathology. Here, we assess the ability of RDoC to rescue psychiatry from its crisis, not only by 1) evaluating its promise of increased validity, but 2) recognizing that psychiatric diagnosis can have an impact on patients’ lives independent of its validity. To assess the former, we delineate possible interpretations of validity relevant to psychiatry, and argue that RDoC faces difficult challenges in achieving what is known as etiopathological validity. To assess the latter, we suggest how the very challenge RDoC faces with respect to validity may counterintuitively serve as a benefit to patients, by reducing the extent to which patients reductionistically re-shape their identities.

The future of faculty psychology depends in no small part on the productive collaboration between neuroscience and psychology. The argument from multiple realization has posed a significant philosophical stumbling block to this quest in the past. Multiple realization should not be taken as an empirical given—establishing that a kind is multiply realizable takes a good deal of work, as Shapiro has been at pains to show; and even when the existence of an MR kind can be verified, the details of its implementation do not suddenly become irrelevant. Structure and function are two sides of the same coin. Thus the multiple realization argument provides no basis for neglecting the discoveries of neuroscience. Faculty psychology’s strength lies precisely in its willingness to work with neuroscience.

The psychophysical identity theory, also known as type-materialism and the central state identity thesis, is supported by a powerful argument based on correlations, and can be defended against the most prominent contemporary objections. These objections include Putnam’s multiple realization argument, the knowledge argument, and the grain argument. The first of these arguments is discussed extensively, and is shown to be vulnerable to several disabling objections. The other two are criticized from the perspective of conceptual dualism. In view of these lines of thought, there is reason to conclude that type-materialism will continue to play a substantial role in science and philosophy for the foreseeable future. But having said this, the paper ends on a cautionary note, pointing to a few objections that may be more substantial than the ones that figure prominently in the literature.

The following chapters aim to provide some classic resources on certain philosophical and scientific assumptions and techniques, such as reduction, supervenience, multiple realization, downwards causation, complexity theory, and chaos. Many of these topics also contain creative contributions to the topics of reduction and emergence, and illustrate the polemics that often surround discussions of emergence. A frequently expressed belief is that, in some sense, physical facts are all the facts that exist and all that need to exist, a belief which lies at the core of the contemporary philosophical position called physicalism. One version of physicalism holds that fundamental physics captures the basic truths about the world and determines everything else in physics as well as in chemistry and in biology.

Type-materialism asserts that every qualitative mental state is identical with a brain state. It is maintained, contrary to Putnam’s multiple realization argument, that qualitative states are strongly correlated with specific brain states, and that such correlations provide a good reason to accept type-materialism. It is also urged that it is possible to undercut various arguments for property dualism, such as the Cartesian modal argument, by appealing to differences between the concepts that we use to record qualitative states (phenomenal concepts) and the concepts we use to register brain states. Another theme is that it is possible to know the qualitative states of others by inductive reasoning, even though the basis of induction involves only a single case.