Philosophical Foundations of Neuroscience. P. M. S. Hacker
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a wide range of psychological powers, which are exercised in the circumstances of life, when we perceive, think and reason, feel emotions, want things, form plans and make decisions. The possession and exercise of such powers define us as the kinds of animals we are. We may enquire into the neural conditions and concomitants for their possession and exercise. This is the task of neuroscience, which is discovering more and more about them. But its discoveries in no way affect the conceptual truth that these powers and their exercise in perception, thought and feeling are attributes of human beings, not of their parts – in particular, not of their brains. A human being is a psychophysical unity, an animal that can perceive, act intentionally, reason and feel emotions, a language-using animal that is not merely conscious, but also self-conscious – not a brain embedded in the skull of a body. Sherrington, Eccles and Penfield conceived of human beings as animals in whom the mind, which they thought of as the bearer of psychological attributes, is in liaison with the brain. It is no advance over that misconception to suppose that the brain is a bearer of psychological attributes.
Talk of the brain’ s perceiving, thinking, guessing or believing, or of one hemisphere of the brain’ s knowing things of which the other hemisphere is ignorant, is widespread among contemporary neuroscientists. This is sometimes defended as being no more than a trivial façon de parler. But that is quite mistaken. For the characteristic form of explanation in contemporary cognitive neuroscience consists in ascribing psychological attributes to the brain and its parts in order to explain the possession of psychological attributes and the exercise (and deficiencies in the exercise) of cognitive powers by human beings.
The ascription of psychological – in particular, cognitive and cogitative – attributes to the brain is, we show, also a source of much further confusion. Neuroscience can investigate the neural conditions and concomitants of the acquisition, possession and exercise of sentient powers by animals. It can discover the neural preconditions for the possibility of the exercise of distinctively human powers of thought and reasoning, of articulate memory and imagination, of emotion and volition. This it can do by patient inductive correlation between neural phenomena and the possession and exercise of psychological powers, and between neural damage and deficiencies in normal mental functions. What it cannot do is replace the wide range of ordinary psychological explanations of human activities in terms of reasons, intentions, purposes, goals, values, rules and conventions by neurological explanations (reductionism is discussed in chapter 13 [16]). And it cannot explain how an animal perceives or thinks by reference to the brain’ s, or some part of the brain’ s, perceiving or thinking. For it makes no sense to ascribe such psychological attributes to anything less than the animal as a whole. It is the animal that perceives, not parts of its brain, and it is human beings who think and reason, not their brains. The brain and its activities make it possible for us – not for it – to perceive and think, to feel emotions, and to form and pursue projects.
While the initial response of many neuroscientists to the accusation of conceptual confusion is to claim that the ascription of psychological predicates to the brain is a mere façon de parler, their reaction to the demonstrable fact that their explanatory theories nontrivially ascribe psychological powers to the brain is sometimes to suggest that this error is unavoidable due to the deficiencies of language. We confront this misconception in chapter 14, where we show that the great discoveries of neuroscience do not require this misconceived form of explanation – that what has been discovered can readily be described and explained in our existing language. We demonstrate this by reference to the much discussed phenomena resultant upon commissurotomy, described (or, we suggest, misdescribed) by Sperry, Gazzaniga and others (§14.3 [§17.3]).
In Part II we investigate the use of concepts of perception, memory, mental imagery, emotion and volition in current neuroscientific theorizing. From case to case we show that conceptual unclarity – failure to give adequate attention to the relevant conceptual structures – has often been the source of theoretical error and the grounds for misguided inferences. It is an error, a conceptual error, to suppose that perception is a matter of apprehending an image in the mind (Crick, Damasio, Edelman), or the production of a hypothesis (Helmholtz, Gregory), or the generation of a 3-D model description (Marr). It is confused – a conceptual confusion – to formulate the binding problem as the problem of combining data of shape, colour and motion to form the image of the object perceived (Crick, Kandel, Wurtz). It is wrong, conceptually wrong, to suppose that memory is always of the past, or to think that memories can be stored in the brain in the form of the strength of synaptic connections ( Kandel, Squire, Bennett). And it is mistaken, conceptually mistaken, to suppose that the investigation of thirst, hunger and lust is an investigation into the emotions ( Rolls) or to think that the function of the emotions is to inform us of our visceral and musculoskeletal state ( Damasio).
The initial reaction to such critical remarks may well be indignation and incredulity. How can a flourishing science be fundamentally in error? How could there be unavoidable conceptual confusion in a well-established science? Surely, if there are problematic concepts, they can easily be replaced by others that are unproblematic and that serve the same explanatory purposes. Such responses betoken a poor understanding of the relation between form of representation and facts represented, and a misunderstanding of the nature of conceptual error. They also betray ignorance of the history of science in general, and of neuroscience in particular.
Science is no more immune to conceptual error and confusion than any other form of intellectual endeavour. The history of science is littered with the debris of theories that were not simply factually mistaken, but conceptually awry. Stahl’ s theory of combustion, for example, was conceptually flawed in ascribing, in certain circumstances, negative weight to phlogiston – an idea that made no sense within its framework of Newtonian physics. Einstein’ s famous criticisms of the theory of electromagnetic aether (the alleged medium by which light was thought to be propagated) were directed not only at the results of the Michelson–Morley experiment, which had failed to detect any effect of absolute motion, but also at a conceptual confusion concerning relative motion involved in the role ascribed to aether in the explanation of electromagnetic induction. Neuroscience has been no exception – as we show in our historical survey. It is true enough that the subject is now a flourishing science. But that does not render it immune to conceptual confusions and entanglements. Newtonian kinematics was a flourishing science, but that did not stop Newton from becoming entangled in conceptual confusions over the intelligibility of action at a distance, or from bafflement (not remedied until Hertz) over the nature of force. So too, Sherrington’ s towering achievement in explaining the integrative action of synapses in the spinal cord, and thereby eliminating, once and for all, the confused idea of a ‘spinal soul’, was perfectly compatible with conceptual confusions concerning the ‘cerebral soul’ or mind and its relation to the brain. Similarly, Penfield’ s extraordinary achievements in identifying functional localization in the cortex, as well as in developing brilliant neurosurgical techniques, were perfectly compatible with extensive confusions about the relation between the mind and the brain and about the ‘highest brain function’ (an idea borrowed from Hughlings Jackson).
In short, conceptual entanglement can coexist with flourishing science. This may appear puzzling. If the science can flourish despite such conceptual confusions, why should scientists care about them? Hidden reefs do not imply that the seas are not navigable, only that they are dangerous. The moot question is how running on these reefs is manifest. Conceptual confusions may be exhibited in different ways and at different points in the investigation. In some cases, the conceptual unclarity may affect neither the cogency of the questions nor the fruitfulness of the experiments, but only the understanding of the results of the experiments and their theoretical implications. So, for example, Newton embarked on the Optics in quest of insight into the character of colour. The research was a permanent contribution to science. But his conclusion that ‘colours are sensations in the sensorium’ demonstrates failure to achieve the kind of understanding he craved. For, whatever colours are, they are not ‘sensations