Paul M. Churchland

Perceptual Plasticity and Theoretical Neutrality: A Reply to Jerry Fodor

The doctrine that the character of our perceptual knowledge is plastic, and can vary substantially with the theories embraced by the perceiver, has been criticized in a recent paper by Fodor. His arguments are based on certain experimental facts and theoretical approaches in cognitive psychology. My aim in this paper is threefold: (1) to show that Fodors views on the impenetrability of perceptual processing do not secure a theory-neutral foundation for knowledge; (2) to show that his views on impenetrability are almost certainly false; and (3) to provide some additional arguments for, and illustrations of, the theoretical character of all observation judgments.

Some Reductive Strategies in Cognitive Neurobiology

A powerful conception of representation and computation — drawn from recent work in the neurosciences — is here outlined. Its virtues are explained and explored in three important areas: sensory representation, sensorimotor coordination, and microphysical implementation. It constitutes a highly general conception of cognitive activity that has significant reductive potential.

Chimerical colors: some phenomenological predictions from cognitive neuroscience

The Hurvich–Jameson (H–J) opponent-process network offers a familiar account of the empirical structure of the phenomenological color space for humans, an account with a number of predictive and explanatory virtues. Its successes form the bulk of the existing reasons for suggesting a strict identity between our various color sensations on the one hand, and our various coding vectors across the color-opponent neurons in our primary visual pathways on the other. But anti-reductionists standardly complain that the systematic parallels discovered by the H–J network are just empirical correspondences, constructed post facto, with no predictive or explanatory purchase on the intrinsic characters of qualia proper. The present paper disputes that complaint, by illustrating that the H–J model yields some novel and unappreciated predictions, and some novel and unappreciated explanations, concerning the qualitative characters of a considerable variety of color sensations possible for human experience, color sensations that normal people have almost certainly never had before, color sensations whose accurate descriptions in ordinary language appear semantically ill-formed or even self-contradictory. Specifically, these “impossible” color sensations are activation-vectors (across our opponent-process neurons) that lie inside the space of neuronally possible activation-vectors, but outside the central ‘color spindle’ that confines the familiar range of sensations for possible objective colors. These extra-spindle chimerical-color sensations correspond to no reflective color that you will ever see objectively displayed on a physical object. But the H–J model both predicts their existence and explains their highly anomalous qualitative characters in some detail. It also suggests how to produce these rogue sensations by a simple procedure made available in the latter half of this paper. The relevant color plates will allow you to savor these sensations for yourself.

Intertheoretic Reduction: A Neuroscientist’s Field Guide

Might psychology someday be reduced to (that is, be exhaustively explained by) computational neurobiology? Many still say no. We approach this question through a brief survey of some prominent intertheoretic reductions drawn from the history of science. A general characterization of reduction is constructed from these, and some important philosophical and methodological lessons are drawn. The five most popular objections to the possibility of a neurobiological reduction of psychology are then addressed, and defeated.

Neural worlds and real worlds

States of the brain represent states of the world. But at least some of the mind–brains internal representations, such as a sensation of heat or a sensation of red, do not resemble the external realities that they represent: mean kinetic energy (temperature) or electromagnetic reflectance (colour). The historical response has been to distinguish between objectively real properties, such as shape and motion, and subjective properties, such as heat and colour. However, this approach leads to trouble. A challenge for cognitive neurobiology is to characterize, in general terms, the relationship between brain models and the world. We propose that brains develop high-dimensional maps, the internal distance relationships of which correspond to the similarity relationships that constitute the categorical structure of the world.

On the reality (and diversity) of objective colors : How color-qualia space is a map of reflectance-profile space

How, if at all, does the internal structure of human phenomenological color space map onto the internal structure of objective reflectance‐profile space, in such a fashion as to provide a useful and accurate representation of that objective feature space? A prominent argument (due to Hardin, among others) proposes to eliminate colors as real, objective properties of objects, on grounds that nothing in the external world (and especially not surface‐reflectance‐profiles) answers to the well‐known and quite determinate internal structure of human phenomenological color space. The present paper proposes a novel way to construe the objective space of possible reflectance profiles so that (1) its internal structure becomes evident, and (2) that structure’s homomorphism with the internal structure of human phenomenological color space becomes obvious. The path is thus reopened to salvage the objective reality of colors, in the same way that we preserved the objective reality of such features as temperature, pitch, and sourness—by identifying them with some objective feature recognized in modern physical theory.

Cognitive neurobiology: a computational hypothesis for laminar cortex

This paper outlines the functional capacities of a novel scheme for cognitive representation and computation, and it explores the possible implementation of this scheme in the massively parallel organization of the empirical brain. The suggestion is that the brain represents reality by means of positions in suitably constitutes phase spaces; and the brain performs computations on these representations by means of coordinate transformations from one phase space to another. This scheme may be implemented in the brain in two distinct forms: (1) as a “phase-space sandwich”, which may explain certain laminar structures, such as cerebral cortex and the superior colliculus; and (2) as a “neural matrix”, which may explain other structures, such as the beautifully orthogonal architecture of the cerebellum.

Conceptual Progress and Word/World Relations: In Search of the Essence of Natural Kinds

The problem of natural kinds forms the busy crossroads where a number of larger problems meet: the problem of universals, the problem of induction and projectibility, the problem of natural laws and de re modalities, the problem of meaning and reference, the problem of intertheoretic reduction, the question of the aim of science, and the problem of scientific realism in general.1 Nor do these exhaust the list. Not sur-

A Deeper Unity: Some Feyerabendian Themes in Neurocomputational Form

By the late 60s, every good materialist expected that epistemological theory would one day make explanatory contact, perhaps even a reductive contact, with a proper theory of brain function. Not even the most optimistic of us, however, expected this to happen in less than fifty years, and most would have guessed a great deal longer. And yet the time has arrived. Experimental neuroscience has revealed enough of the brain’s microphysical organization, and mathematical analysis and computer simulation have revealed enough of its functional significance, that we can now address epistemological issues directly. Indeed, we are in a position to reconstruct, in neurocomputational terms, issues in the philosophy of science specifically. This is my aim in what follows.

How parapsychology could become a science

An important methodological argument is outlined in support of general theoretical challenges to the dominant materialist paradigm. The idea is that the empirical inadequacies of a dominant theory can be hidden from view by various factors, and will emerge from the shadows only when viewed from the perspective of a systematic conceptual alternative. The question then posed is whether parapsychology provides a conceptual alternative adequate to this task. The provisional conclusion drawn is that it does not. Some further consequences are drawn from this concerning the experimental side of the parapsychological tradition.