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do not realise why so many of the deepest problems of philosophy have to crop up, in slightly different forms, every generation and have to be tackled de novo by each generation. This we try to explain by reference to the fact that the potentiality for conceptual confusion is buried deep in our language. Such confusions can be eliminated for a few decades by painstaking conceptual analysis. But they will rise again, as younger generations fall into the same traps. Sense data died under critical onslaught in the 1950s and 1960s, but by the end of the century internal representations arose phoenixlike from their ashes.

      Numerous scientists find puzzling the thought that a priori reflection can have any bearing on experimental science, and that experimental science, while it can present new conceptual problems for connective analysis, cannot show logico-grammatical analyses to be mistaken. It is surely impossible that a few minutes’ armchair reflection on the use of a couple of words in English should be able to trump painstaking experiments of the greatest sophistication, using instruments that probe the functioning of the brain, that are successfully repeated all over the world. It seems equally baffling to suggest that a well-constructed neuroscientific experiment should not be able to prove false the grammatical conventions of a prescientific language concerned with perception, thought, affection and will in all their forms. Logico-grammatical analysis investigates mere words, but neuroscientists are concerned with reality. Cartesian dualism, it is argued, was shown to be false by the discovery of the law of conservation of momentum. That an immaterial substance might affect the total quantity of momentum would violate the laws of physics.

This is mistaken. Cartesian dualism is not shown to be false by the advance of science, for science can show something to be false only if it makes sense. If it makes sense then it is intelligible that it be true even though it happens not to be. If the Cartesian mind were able to change the direction of motion of the body by acting on the pineal gland, then the so called system of the physical universe would not be closed, as philosophers of science commonly suppose it to be, and the Law of Conservation of Momentum would be false. But the flaw in Cartesian dualism (or, more generally, substance-dualism) is not that it is false but that it is not coherent. It makes no sense, because the idea of an immaterial, spiritual substance is incoherent. It lacks both synchronic and diachronic criteria of identity. The idea that an immaterial substance might be an active agent in the material world, with the powers to causally affect the pineal gland by acting on it thereby releasing animal spirits into the nerves, makes no sense. It is not a false theory but an incoherent conjecture.

      Conceptual analysis is to neuroscience what the differential calculus is to physics: a neuroscientist cannot do without it, whether he likes it or not. He can take for granted a received conception, often rooted in past defective analyses (e.g. by William James or by von Helmholtz ), or he can confront the received assumptions and reflect on them. It is for those striving to think for themselves that we offer our work as a set of guidelines. For on most of the major themes of cognitive neuroscientific research we try to provide the major conceptual characterizations, depicting the logical geography of the domain.

Conceptual mistakes have real consequences, for our concepts unavoidably guide both practice and interpretation. These consequences in neuroscience are of at least three kinds. First, if a neuroscientific experiment misconstrues its actual subject matter, then no matter how internally consistent it is, its results will have no practical, real-world implications, since its results are hermetic to the misguided framework within which the experiment is constructed. An example here is Libet’ s conception of voluntary action, which has not in practice stopped anyone from changing their behaviour in the several hundred millisecond interval preceding the movement with regard to which we are allegedly mere automata. Second, an incoherent scientific theory built on perfectly valid data will fail in inductive, predictive reasoning, just as an equation in physics that contains a covert division by zero will fail in its predictive use. Once the incoherence has been realized, one need not wait for the zero values to be entered into the equation to know that a theory based on such an equation is going to be worthless. Hence investigations of the neuroscience of memory that rest on the assumption that memory is of or about the past, or that memory is exhibited by any change of behaviour consequent upon prior experience, can be rejected in advance of any experiment. For memory is acquired in the past, but it need not be of the past – it may be of or about the present, the future, omnitemporal or atemporal; and wricking one’ s ankle and thereafter limping is not remembering anything. Third, whether predictive or not, a scientific theory that is conceptually flawed cannot be explanatory. For explanation, even more than prediction, depends on the coherence and integrity of the conceptual framework within which it is constructed, no less than upon the empirical data it brings to bear on the explanandum. Of course, the empirical consequences of conceptual errors in neuroscience are not typically immediately obvious, especially when widely accepted by groups of working neuroscientists. However, such errors are not stochastic: if something makes no sense, there is no chance that it will later spontaneously acquire sense as the experiments unfold. It is true that in the past important discoveries have been made despite incoherent theories. But that is not a recommendation for incoherence. Incoherence is not an infantile disease that neuroscientific theories catch before they mature into received neuroscientific wisdom.

      Does all this mean that neuroscientists have to study philosophy or to become philosophers? No – there are great swathes of philosophy, such as metaphysics, logic, philosophy of mathematics, or moral and political philosophy that are of no concern to the neuroscientist. Nevertheless, many of the conceptual structures presupposed in neuroscientific research and the specific conceptual forms invoked are, by their nature, highly problematic. For they unavoidably link the conceptually heterogeneous domains of the behavioural, the psychological and the neural. Furthermore, neuroscientists are sometimes required to extend existing concepts or to introduce new concepts for specialized purposes. It is all too easy to do so in inconsistent and incoherent ways. It is desirable that neuroscientists be familiar with connective analytic methods in order to sharpen their sensitivity to conceptual unclarities, errors and confusions. They must be able to realize that, for example, memory need not be of the past, that one cannot order someone to be conscious of something, that if one is conscious of something’ s being so, then it follows that it is so, that something may be voluntary without being intentional or intentional without being voluntary, and so on. They cannot stand aloof from conceptual questions or refrain from committing themselves to conceptual forms.

      It will come as no surprise to those who have read the first edition of this book that a spirit hovers over its arguments: the spirit of Ludwig Wittgenstein. Why Wittgenstein rather than Popper (who inspired Eccles ) or even Locke (who inspired von Helmholtz )? Because Wittgenstein’ s reflections on the philosophy of psychology surpass anything previously achieved in this domain of philosophical thought. Our conceptual analyses in this book echo and elaborate Wittgenstein’ s not because we are fond of Wittgenstein but because his intellectual approach in this domain is precisely what is needed by cognitive neuroscience. Philosophy of psychology has to elucidate the conceptual relations between the behavioural and the ‘inner’, ‘mental’ or ‘psychological’. It has to account for the conceptual structures that inform the asymmetries between the first-person utterance and the third-person description of ‘experience’ or ‘states of consciousness’. Wittgenstein broke with a long tradition of conceptual confusion characteristic of both rationalist and empiricist thought, indeed a tradition dating back to antiquity. He ploughed up the field of philosophical thought afresh. Cognitive neuroscience was firmly planted in that field, with roots reaching down to the late fifteenth and sixteenth centuries, as we describe in chapter 1. It has to cope with a subject matter that straddles the behavioural and the ‘inner’, although here the ‘inner’ is neural and cortical. The basic observation statements of the science are what people do and say, and it is these that need to be related to an ‘inner’. Here too there is an illusion that just as introspection seems to bypass behaviour and give one direct access to an ‘inner’, so too positron emission tomography ( PET ) and functional magnetic resonance imaging (f MRI ) give neuroscientists the illusion that they can bypass behaviour and study the ‘real thing’ directly. At last, as one well-known neuroscientist exclaimed, we can ‘actually see

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