Sektionsredner

A central focus of contemporary philosophy of mind is the causal exclusion problem (Kim, 1998). Given the premise that mental properties strongly supervene on physical properties and the premise of the causal, nomological and explanatory completeness of the physical domain, the causal exclusion problem turns out to be a strong argument in favour of the psychophysical identity thesis. Then, all there is in the world is identical with physical properties that can also make true mental descriptions.

Therefore, the causal exclusion problem supports the reductionism in philosophy of mind. This means, it suggests the possibility to reduce mental description to physical ones. However, the multiple realization argument (MR) is generally considered as a conclusive objection against theory reduction by maintaining that bi-conditional links between concepts of different sciences cannot be established (as required by the classical Nagalian account of reduction). MR is right in pointing out that mental concepts are not co-extensional with any physical or neuroscientific concepts, since physically different individuals can fall under the same mental description. MR speaks therefore against theory reduction and stands clearly in conflict with the above mentionned suggestion.

I shall take Kim’s argument as a starting point and move on to consider MR from a new perspective that does not contradict reductionism. My talk is based on a new model of inter-theoric reduction by means of functionally defined sub-concepts due to Esfeld & Sachse (Esfeld and Sachse, 2007), which is designed to escape the anti-reductionist consequence of MR. The sub-concepts strategy proceeds in three steps: first, if two physical entities p1 and p2 fall under a functional concept F, there is a systematic difference in the way in which p1 and p2 produce the characteristical effect of F. Second, there are physically possible conditions under which those side-effects manifest themselves in a functional salient way. Third, on the basis of those salient manifestations, one can constructs sub-concepts F1 and F2 of F within a functional vocabulary. We thus obtain the co-extensionality between functionally defined sub-concepts and physical concepts as required in the nagalian account.

The sub-concept strategy has been applied in detail to the relation between classical and molecular genetics (Sachse, 2007) and opens crucial issues whether it works for the mind-brain case. I shall illustrate how this model can be applied to reduce folk psychology to neuropsychology, using a classical example of cognitive sciences, namely the disconnection syndrome. This one picks out a set of behavioural abnormalities arising, from the neurological point of view, from injuries to, or from a total lack of corpus callosum. This one is a large strip linking both hemispheres of mammalians brains and allowing information exchange between the two half-brains.

Behavioural issues of commissurotomy have been extensively studied since the re-introduction of this type of surgery as an elective treatment of epilepsy. The most surprising result is the apparent lack of change with respect to the daily life of patients. Indeed, one needs specific cognitive tests to detect from a behavioural perspective differences between split-brain patients and ordinary subjects (Kolb and Whishaw, 2003). On the one hand (step 1), since split-brain patients behave normally, usual functionalized mental states can be ascribed to them in the same way as to ordinary subjects. On the other hand (step 2), specific cognitive tests enable us to discriminate between ordinary and split-brain individuals on purely behavioural criteria. The claim is that behavioural particularities of split-brain patients can thus be captured in the vocabulary of a functionalized folk-psychology. This fact enables us (step 3) to construct sub-concepts F1 and F2 of any mental state F shared by split-brain and ordinary individuals. F1 and F2 are still instances of F since they contain the functional definition of F, but they capture also the side-effects produced by a particular realizer by additional functional specifications. Against this backround, a functionalized folk psychology can in principle be reduced to neuropsychology, since neuropsychology is devoted to the interaction between neurological specificities and observable behaviour.

ESFELD, M. and SACHSE, C. (2007), 'Theory reduction by means of functional sub-types', International Studies in the Philosophy of Science, 21.

KIM, J. (1998), Mind in a physical world. An essay on the mind-body problem and mental causation. Cambridge (Massachusetts): MIT Press.

KOLB, B. and WHISHAW, I.Q. (2003), Fundamentals of human neuropsychology. New York: Worth.

SACHSE, C. (2007), Reductionism in the Philosophy of sciences. Frankfurt (Main): Ontos-Verlag.