Patricia Churchland

States of the brain represent states of the world. A puzzle arises when one learns that at least some of the mind/brain’s internal representations, such as a sensation of heat or a sensation of red, do not genuinely resemble the external realities they allegedly represent: the mean kinetic energy of the molecules of the substance felt (temperature) and the mean electromagnetic reflectance profile of the seen object (color). The historical response has been to declare a distinction between objectively real properties, such as shape motion and mass, and merely subjective properties, such as heat, color and smell. This hypothesis leads to trouble. A challenge for cognitive neurobiology is to characterize, in suitably general terms, the nature of the relationship between brain models and the world modeled. We favor the hypothesis that brains develop high-dimensional maps whose internal relations correspond in varying degrees of fidelity to the enduring causal structure of the world. From this perspective, the basic epistemological relation is not “single-percept to single- external-feature” but rather “background-brain-maps to causal-domain-portrayed.

Any mention of the relationship, still poorly understood, between body (or brain) and mind invariably invokes the name of Descartes, who is often thought of as the father of modern philosophy and perhaps of neurophilosophy. Although a native of the heart of France (the region around Tours), Rene Descartes travelled widely, as everyone knows, especially to Holland and Sweden. It should come as no surprise, that the Congress of Neurophilosophy and Alzheimer's Disease was the first in the series of Fondation Ipsen Colloques Medecine et Recherche to be held outside France. The meeting was held in San Diego (California) on January 11, 1991. This venue was chosen for a number of reasons. The University of California San Diego is without doubt one of the most dynamic universities today. A good number of friends of the Fondation Ipsen who have taken part as speakers in previous conferences are based there. Patricia Churchland, whose publications have helped "launch" the term "neurophilosophy", also teaches there. The choice of this particular venue gave us the welcome opportunity of benefiting directly during the conference from the participation of many eminent (including some Nobel Prize-winning) scientists, including biochemists, neuro scientists and "alzheimerologist", psychologists, cognitive science specialists and philosophers.

The explanation of a child's discriminate responses to his environment turns on ascribing to the child a perceptual discrimination which counts certain things as more similar to one another than to some other thing. As Quine forcefully puts it:If an individual is to learn at all, differences in degree of similarity must be implicit in his learning pattern. Otherwise any response, if reinforced, would be conditioned equally and indiscriminately to any and every future episode, all these being equally similar.Now for those determined to cleave to behaviourist canons, the problem is to use ‘perceptual similarity’ in explaining the subject's discriminating responses in a way which does not imply the existence of mental states and entities. What this really means is that the behaviourist must reconstruct the notion of ‘perceptual similarity', purifying it of its mentalistic dimension. So long as physicalism is a reasonable position, and while we are awaiting and abetting the neurophysiological millennium, the behaviourist's project is of significant moment. Now in Word and Object Quine does not seriously attempt to provide behavioural criteria for a subject's perceiving similarities, and he provisionally permits himself the mentalistic idiom he avows finally to eschew.

Beginning with Thomas Nagel, various philosophers have propsed setting conscious experience apart from all other problems of the mind as ‘the most difficult problem’. When critically examined, the basis for this proposal reveals itself to be unconvincing and counter-productive. Use of our current ignorance as a premise to determine what we can never discover is one common logical flaw. Use of ‘I-cannot-imagine’ arguments is a related flaw. When not much is known about a domain of phenomena, our inability to imagine a mechanism is a rather uninteresting psychological fact about us, not an interesting metaphysical fact about the world. Rather than worrying too much about the meta-problem of whether or not consciousness is uniquely hard, I propose we get on with the task of seeing how far we get when we address neurobiologically the problems of mental phenomena.

Anydomainofscientificresearchhasitssustainingorthodoxy. Thatis, research on a problem, whether in astronomy, physics, or biology, is con- ducted against a backdrop of broadly shared assumptions. It is these as- sumptionsthatguideinquiryandprovidethecanonofwhatisreasonable-- of what "makes sense." And it is these shared assumptions that constitute a framework for the interpretation of research results. Research on the problem of how we see is likewise sustained by broadly shared assump- tions, where the current orthodoxy embraces the very general idea that the business of the visual system is to create a detailed replica of the visual world, and that it accomplishes its business via hierarchical organization and by operatingessentiallyindependently of other sensorymodalitiesas well as independently of previous learning, goals, motor planning, and motor execution.