Online research in philosophy

I sketch a theory of cognitive representation from recent "connectionist" cognitive science. I then argue that (i) this theory is reducible to neuroscientific theories, yet (ii) its kinds are multiply realized at a neurobiological level. This argument demonstrates that multiple realizability alone is no barrier to the reducibility of psychological theories. I conclude that the multiple realizability argument, the most influential argument against psychophysical reductionism, should be abandoned.

b>: This article explains the concept of multiple realizability and its role in the philosophy of mind. In particular, I consider what is required for the multiple realizability of psychological kinds, the relevance of multiple realizability to the reducibility and autonomy of psychology, as well as further refinements of the concept that would prove helpful.

Reductionism is often understood to include two theses: (1) every singular occurrence that the special sciences can explain also can be explained by physics; (2) every law in a higher-level science can be explained by physics. These claims are widely supposed to have been refuted by the multiple realizability argument, formulated by Putnam (1967, 1975) and Fodor (1968, 1975). The present paper criticizes the argument and identifies a reductionistic thesis that follows from one of the argument's premises.

Multiple Realizability (MR) must still be regarded as one of the principal arguments against type reductionist accounts of higher-order properties and their special laws. Against this I argue that there is no unique MR but rather a multitude of MR categories. In a slogan: MR is itself “multi-realized”. If this is true then we cannot expect one unique reductionist strategy against MR as an anti-reductionist argument. The main task is rather to develop a taxonomy of the wide variety of MR cases and to sketch possible reductionist answers for each class of cases. The paper outlines some first steps in this direction.

Bechtel and Mundale (1999) argue that multiple realizability is not plausible. They point out that neuroscientists assume that psychological traits are realized similarly in homologous brain structures and contend that a biological aspect of the brain that is relevant to neuropsychological state individuation provides evidence against multiple realizability. I argue that Bechtel and Mundale adduce the wrong sort of evidence against multiple realizability. Homologous traits do not provide relevant evidence. It is homoplasious traits of brains that can provide evidence for or against multiple realizability.

Some scientists and philosophers have claimed that there is a converse to multiple realizability. While a given higher-level property can be realized by different lower-level properties (multiple realizability), a given lower-level property can in turn serve to realize different higher-level properties (this converse I dubbed the unfortunately obscure "constructival plasticity" to emphasize the constructive metaphysics involved when realizing properties generate realized properties in the stated way). I begin by defining multiple realizabilty in a formal way, then turn to the relation in question. By my analysis, for the converse claim to be true, a lower-level property G1 that realizes a higher-level F must be taken in conjunction with some other base condition G2 so that a difference in G2 allows G1 to determine some other higher-level property E but not F (otherwise there would be violations of supervenience). The realization law thus has the form: (G1 & G2) => F. As such, the base property G1 is insufficient by itself to produce F. It is an insufficient but necessary part of a sufficient condition. I also point out that this makes the realization base property an INUS condition, if combined with multiple realizability. Specifically, if F is multiply realized by properties other than the pair G1 and G2, then G1 is an insufficient but necessary part of an unnecessary but sufficient condition.

While the concept of multiple realizability is widely used, it is seldom rigorously characterized. This paper defends a liberal conception of multiple realizability as sameness of type through _any_ differences in the (lower-level) conditions that give rise to instances of that type. This kind of “sameness through difference” is contrasted with another type of asymmetric dependency relation between properties, multiple _specification_. This liberal conception is then defended from objections, and it is augmented by a concept of relativized multiple realizability. The last section presents a survey of the ontological, explanatory, and methodological consequences of this analysis of multiple realizability.

For nearly thirty years, there has been a consensus (at least in English-speaking countries) that reductionism is a mistake and that there are autonomous special sciences. This consensus has been based on an argument from multiple realizability. But Jaegwon Kim has argued persuasively that the multiple realizability argument is flawed.1 I will sketch the recent history of the debate, arguing that much --but not all--of the anti-reductionist consensus survives Kim's critique. This paper was originally titled "Anti-Reductionism Strikes Back", but in the course of writing the paper, I came to think that the concepts used in the debate would not serve either position very well.

In the literature on multiple realizability and the identity theory, cases of neural plasticity have enjoyed a very limited role. The present paper attempts to remedy this small influence by arguing that clinical and experimental evidence of quite extensive neural reorganization offers compelling support for the claim that psychological kinds are multiply realized in neurological kinds, thus undermining the identity theory. In particular, cases are presented where subjects with no measurable psychological deficits also have vast, though gradually received, neurological damage. Common objections and concerns are also discussed and rejected.