Nigel Thomas

Posttranslational modification of proteins and peptides is important for diverse biological processes in plants and animals. The paucity of heterologous expression systems for PTMs and the technical challenges associated with chemical synthesis of these modified proteins has limited detailed molecular characterization and therapeutic applications. Here we describe an optimized system for expression of tyrosine-sulfated proteins in Escherichia coli and its application in a bio-based crop protection strategy in rice.

This ambitious work apparently has two main aims. The first is to provide a survey of the currently burgeoning field of "Consciousness Studies", presented via the extended metaphor of a horse race whose winning post is a full scientific explanation of consciousness. The second, which receives much more space, is to present Taylor's own cognitive/neuroscientific theory, dubbed "relational consciousness", and to persuade us that it should be the odds-on favourite to win. Neither aim is very well realized

here was a brief inaugural session of the Association for the Scientific Study of Consciousness during the Psychonomic Society Conference in Los Angeles in November 1995, but the first full conference of the Association was held this June in the very pleasant surroundings of the Claremont Colleges. Being at this conference was very different from being at ‘Tucson II’ the previous year. This was a less ballyhooed, more intimate event, maybe less exciting, and less intellectually eclectic, but also perhaps more conducive to serious scientific exchange. Certainly the roster of speakers was replete with luminaries of the consciousness studies movement, and highly respected names from psychology, neuroscience and philosophy: Christof Koch, Bernard Baars, Ned Block, Philip Merikle, Daniel Schacter, Larry Jacoby, Walter Freeman, Valerie Hardcastle, both Churchlands, Melvyn Goodale, Owen Flanagan . . . to unfairly pick out just a few

Classical and medieval writers had no term for consciousness in anything like the modern sense, and their philosophy seems not to have been troubled by the mind-body problem. Contemporary eliminativists find strong support in this fact for their claim that consciousness does not exist, or, at least, is not an appropriate scientific explanandum. They typically hold that contemporary conceptions of consciousness are artefacts of Descartes' (now outmoded) views about matter and his unrealistic craving for epistemological certainty. Essentially, they say, our belief in consciousness is a residue of once pressing, but now irrelevant, intellectual tensions between religion and the rising new science of the Early Modern period. With the attempts of Descartes and his successors to resolve these tensions, Western thought began down a track toward the conceptual cul-de-sac of the "hard problem". Plausibly, the problem will only be (dis)solved, and the onward march of science assured, when we are able to shake off the pervasive influence of the Cartesian tradition in a way that goes far beyond the mere rejection of dualism. But when we do so, eliminativists contend, the distinctively Cartesian notion of consciousness will simply drop out of our world-picture, like phlogiston or the vital entelechy

Traditionally ‘imagination’ primarily denotes the faculty of mental imagery, other usages being derivative. However, contemporary philosophers commonly hold it to be a polysemous term, with several unrelated senses. This effectively eliminates this culturally important concept as an appropriate explanandum for science, and paves the way for a thoroughgoing eliminative materialism. White challenges both these views of imagination, arguing that ‘imagine’ never means ‘suppose,’ ‘believe,’ ‘pretend’ or ‘visualize,’ that imagery may occur without imagination, and that the true sense of ‘imagine’ is (roughly) ‘think of as possibly being so.’ I defend a version of the traditional view. The disseverance of imagination from imagery is motivated by an implicit version of the theory of mental images as pictures. Other contemporary scientific theories of imagery do not entail it. I defend a view of imagery as arising from the interpretative aspect of perception (‘seeing-as’) and connect this, and our contemporary concept of imagination, to the root Aristotelian concept of φαντασία.This captures the association between imagination and creativity, and reveals the coherence of the concept, more plausibly than White’s theory.

The concepts of imagination and consciousness have, very arguably, been inextricably intertwined at least since Aristotle initiated the systematic study of human cognition . To imagine something is ipso facto to be conscious of it , and many have held that our conscious thinking consists largely or entirely in a succession of mental images, the products of imagination . A venerable tradition also regards perceptual experiences, the main focus of most recent work on consciousness, as products of the imagination, whose primary function is to integrate sensory inputs and render them meaningful . As Coleridge famously put it, primary imagination is 'the living power and prime agent of all human perception'. A better understanding of imagination is likely to deepen our insight into the nature of consciousness

This article was written as a commentary on a target article by Peter W. Ross entitled "The Location Problem for Color Subjectivism" [Consciousness and Cognition 10(1), 42-58 (2001)], and is published together with it, and with other commentaries and Ross's reply. If you or your library have the necessary subscription you can get PDF versions of the target article, all the commentaries, and Ross's reply to the commentaries here. However, I do not think that it is by any means essential for you to have read Ross's piece in order to understand this one. Ross defends a view called "color physicalism" or color realism that holds (simplifying somewhat) that colors are real physical properties (in typical cases, spectral reflectances of object surfaces). This is in opposition to what is probably a more widely held "subjectivist" view of color, holding that color qualities really exist only in the mind. In my commentary I suggest that a realist view of qualitative properties, such as Ross's, together with a direct, active view of perception, and a concept of "extended mind" (Clark & Chalmers, 1998) may provide the materials for a real solution to the notorious hard problem of consciousness. I sketch this solution in outline. - N.J.T.T

Until a few years ago, Cognitive Science was firmly wedded to the notion that cognition must be explained in terms of the computational manipulation of internal representations or symbols. Although many people still believe this, the consensus is no longer solid. Whether it is truly threatened by connectionism is, perhaps, controversial, but there are yet more radical approaches that explicitly reject it. Advocates of "embodied" or "situated" approaches to cognition (e.g., Smith, 1991; Varela _et al_ , 1991, Clancey, 1997) argue that thought cannot be understood as entirely internal. Furthermore, it is argued that autonomous robots can be designed to behave more intelligently if representationalist programming techniques are avoided (Brooks, 1991), and that the way our brains control our behavior is better understood in terms of chaos and dynamical systems theory rather than as any sort computation (e.g., Freeman & Skarda, 1990; Van Gelder & Port, 1995; Van Gelder, 1995; Garson, 1996)

Traditionally ‘imagination’ primarily denotes the faculty of mental imagery, other usages being derivative. However, contemporary philosophers commonly hold it to be a polysemous term, with several unrelated senses. This effectively eliminates this culturally important concept as an appropriate explanandum for science, and paves the way for a thoroughgoing eliminative materialism. White challenges both these views of imagination, arguing that ‘imagine’ never means ‘suppose,’ ‘believe,’ ‘pretend’ or ‘visualize,’ that imagery may occur without imagination, and that the true sense of ‘imagine’ is ‘think of as possibly being so.’ I defend a version of the traditional view. The disseverance of imagination from imagery is motivated by an implicit version of the theory of mental images as pictures. Other contemporary scientific theories of imagery do not entail it. I defend a view of imagery as arising from the interpretative aspect of perception and connect this, and our contemporary concept of imagination, to the root Aristotelian concept of φαντασία.This captures the association between imagination and creativity, and reveals the coherence of the concept, more plausibly than White’s theory

This book is a philosopher's examination of the dispute, which raged amongst cognitive psychologists in the 1970s, and has continued to sputter on since, about the nature of mental imagery. As Tye sees things (and, indeed, as the textbooks generally have it) on the one side of the issue we find Stephen Kosslyn and certain close associates, arguing that mental images are best understood on analogy with pictures; and on the other side we find Zenon Pylyshyn, ably seconded by Geoffrey Hinton, arguing that the pictorial analogy is thoroughly misleading, and should be replaced by an analogy to descriptions. Tye's consideration of this debate, attempting to clarify and arbitrate a tangled mess of argument and to explore the implications of what he takes to be the proper outcome, is generally excellent. If you want to understand the strengths of the arguments of Kosslyn, Pylyshyn, and their allies, then this book is to be recommended very warmly.

Galton and subsequent investigators find wide divergences in people's subjective reports of mental imagery. Such individual differences might be taken to explain the peculiarly irreconcilable disputes over the nature and cognitive significance of imagery which have periodically broken out among psychologists and philosophers. However, to so explain these disputes is itself to take a substantive and questionable position on the cognitive role of imagery. This article distinguishes three separable issues over which people can be "for" or "against" mental images. Conflation of these issues can lead to theoretical differences being mistaken for experiential differences, even by theorists themselves. This is applied to the case of John B. Watson, who inaugurated a half-century of neglect of image psychology. Watson originally claimed to have vivid imagery; by 1913 he was denying the existence of images. This strange reversal, which made his behaviorism possible, is explicable as a "creative misconstrual" of Dunlap's "motor" theory of imagination.

Twentieth century philosophy and psychology have been peculiarly averse to mental images. Throughout nearly two and a half millennia of philosophical wrangling, from Aristotle to Hume to Bergson, images (perceptual and quasi-perceptual experiences), sometimes under the alias of "ideas", were almost universally considered to be both the prime contents of consciousness, and the vehicles of cognition. The founding fathers of experimental psychology saw no reason to dissent from this view, it was commonsensical, and true to the lived experience of conscious thinking. However, early in this century, just about when the behaviorist revolution in psychology was loudly declaring the scientific illegitimacy of any attempt to study consciousness, and the concomitant non-existence of imagery (Watson, 1913; see Thomas, 1989), philosophy was undergoing its "linguistic turn", a turn to seeing philosophy as essentially about language rather than the world, even the 'inner' world. For decades, the very concept of the mental image was suspect, and it was certainly banished from playing any major role in theories of mind and of thinking. Ralph Ellis' Questioning Consciousness, together with the recent speculations of certain influential neuroscientists (Edelman, 1992; Damasio, 1994), may be signaling the end this unusual era.

Not long ago, I received an email from a man who had been trying to get his seven-year-old son interested in science, and teach him a little bit about the workings of the brain. He had been showing his son one of those diagrams of a brain with various regions labeled as "speech center," vision center," and the like (something similar to this, I suppose), when the little boy suddenly asked, "Daddy, which part of the brain does imagination come from?". It was not on the diagram, and the father, although he studied human biology at college, realized he did not know the answer. As we do these days, he got on the internet to try to find out. It was not as easy as he might have expected. "Imagination" is certainly a word that is found on a lot of web pages, and there are plenty that seem to be devoted to celebrating or promoting it, but very few of them seem to have anything at all to say about what it is, how it works, or where in the brain it might be implemented. Eventually, he found his way to this site. Even here, however, he could find no straightforward answer to his son's apparently straightforward question. (The truth is, the question is not nearly as straightforward as it appears.) He thought I might be a good a person to ask, however, and sent me an email. What follows is a lightly revised version of the reply I sent. It is not written in terms that a seven-year-old could understand (I am not clever enough to do that), but neither is it pitched at the professional, academic level of most of the material on this site. I would like to think that it answers the question (inasmuch as it can be answered in the current state of scientific knowledge) in a way that a layperson should be able to understand, and that they might then be able to explain to a curious and intelligent child. If you want to know the detailed reasons, and see the citations to the scientific literature, that justify the claims made here, you can find them in the other articles on this site..

Since the publication of my "Are Theories of Imagery Theories of Imagination? An _Active Perception_ Approach to Conscious Mental Content,", a good deal of published material has appeared or has come to my attention that either provides additional support for the Perceptual Activity Theory PA theory) of mental imagery presented in ATOITOI, or that throws further doubt on the rival theories that are criticized there. Other relevant evidence was not mentioned in ATOITOI because I lacked the space for a proper explanation of its relevance. I hope eventually to write and publish a new account of " PA " theory, that will make use of much of this material. In the meantime this page provides citations to the "new" support, and discussion sections that briefly explain the relevance of the cited material. Quite apart from presenting new lines of supporting evidence and argument, I hope this page will help to clarify many aspects of

Classical and medieval writers had no term for consciousness in anything like the modern sense, and their philosophy seems not to have been troubled by the mind-body problem. Contemporary eliminativists find strong support in this fact for their claim that consciousness does not exist, or, at least, is not an appropriate scientific explanandum. They typically hold that contemporary conceptions of consciousness are artefacts of Descartes' (now outmoded) views about matter and his unrealistic craving for epistemological certainty. Essentially, they say, our belief in consciousness is a residue of once pressing, but now irrelevant, intellectual tensions between religion and the rising new science of the Early Modern period. With the attempts of Descartes and his successors to resolve these tensions, Western thought began down a track toward the conceptual cul-de-sac of the "hard problem". Plausibly, the problem will only be (dis)solved, and the onward march of science assured, when we are able to shake off the pervasive influence of the Cartesian tradition in a way that goes far beyond the mere rejection of dualism. But when we do so, eliminativists contend, the distinctively Cartesian notion of consciousness will simply drop out of our world-picture, like phlogiston or the vital entelechy

Stich & Ravenscroft (1994) have argued that (contrary to most people's initial assumptions) a simulation account of folk psychology may be consistent with eliminative materialism, but they fail to bring out the full complexity or the potential significance of the relationship. Contemporary eliminativism (particularly in the Churchland version) makes two major claims: the first is a rejection of the orthodox assumption that realistically construed propositional attitudes are fundamental to human cognition; the second is the suggestion that with the advancement of scientific understanding of the mind it will be possible to entirely eliminate the mentalistic and intentional from our ontology, thus dissolving the mind-body problem. The first claim (which has been argued in detail) supplies the principal grounds for accepting the second, much more ambitious and significant, claim. Robert Gordon's (1995, 1996, 2000) radical simulation theory of "folk psychology", proposed initially (Gordon, 1986) as an alternative to "theory theory" accounts of self and interpersonal understanding, but subsequently developing into a quite general challenge to symbolic computational accounts of mind, is not merely consistent with, but actually provides considerable additional support for, the first eliminativist claim. However, although radical simulationism has no use for reified propositional attitudes, it relies on another family of mentalistic and intentional notions, including perspective taking, "seeing as", pretending, imagery, and, most centrally, imagination. It is thus inconsistent with eliminativist metaphysical ambitions. Nevertheless, from this perspective the mind-body problem is transformed. Its solution no longer depends on accounting directly for the intentionality of the attitudes, but rather on accounting for the intentionality of imagination. Although standard accounts of imagination derive its intentionality from that of the attitudes, the recently proposed "perceptual activity" theory of imagery and imagination (Thomas, 1999) can provide a direct account of the intentionality of imagination that is consistent with physicalism..

A theory of the structure and cognitive function of the human imagination that attempts to do justice to traditional intuitions about its psychological centrality is developed, largely through a detailed critique of the theory propounded by Colin McGinn. Like McGinn, I eschew the highly deflationary views of imagination, common amongst analytical philosophers, that treat it either as a conceptually incoherent notion, or as psychologically trivial. However, McGinn fails to develop his alternative account satisfactorily because (following Reid, Wittgenstein and Sartre) he draws an excessively sharp, qualitative distinction between imagination and perception, and because of his flawed, empirically ungrounded conception of hallucination. His arguments in defense of these views are rebutted in detail, and the traditional, passive, Cartesian view of visual perception, upon which several of them implicitly rely, is criticized in the light of findings from recent cognitive science and neuroscience. It is also argued that the apparent intuitiveness of the passive view of visual perception is a result of mere historical contingency. An understanding of perception (informed by modern visual science) as an inherently active process enables us to unify our accounts of perception, mental imagery, dreaming, hallucination, creativity, and other aspects of imagination within a single coherent theoretical framework.

Mental imagery (varieties of which are sometimes colloquially refered to as “visualizing,” “seeing in the mind's eye,” “hearing in the head,” “imagining the feel of,” etc.) is quasi-perceptual experience; it resembles perceptual experience, but occurs in the absence of the appropriate external stimuli. It is also generally understood to bear intentionality (i.e., mental images are always images of something or other), and thereby to function as a form of mental representation. Traditionally, visual mental imagery, the most discussed variety, was thought to be caused by the presence of picturelike representations (mental images) in the mind, soul, or brain, but this is no longer universally accepted