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

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

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

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.

Philosopher's zombies are hypothetical beings behaviorally, functionally, and perhaps even physically indistinguishable from normal humans, but who lack our consciousness. Many people seem to be convinced that such zombies are a real conceptual possibility, and that this bare possibility entails that understanding human consciousness must remain forever beyond the reach of science. However, the conceptual entailments of zombiehood have not been sufficiently examined. This brief article shows that any way of understanding the behavior of zombies that does in fact support the suggested entailment, leads to contradictions and absurdities. Zombies are _not_ conceptually possible

Commentary on "On Specification and the Senses," by Thomas A. Stoffregen and Benoît G. Bardy: Behavioral and Brain Sciences, 24, 195-261 (2001).
The target article's value lies not in its defence of specification, or the "global array" concept, but in its challenge to the paradigm of 5+ senses, and its examples of multiple receptor types cooperatively participating in specific information pick-up tasks. Rather than analysing our perceptual endowment into 5+ senses, it is more revealing to type perceptual systems according to task.

The concepts of imagination and consciousness have, very arguably, been inextricably intertwined at least since Aristotle initiated the systematic study of human cognition (Thomas, 1998). To imagine something is ipso facto to be conscious of it (even if the wellsprings of imaginative creativity are in the unconscious), and many have held that our conscious thinking consists largely or entirely in a succession of mental images, the products of imagination (see, e.g., Damasio, 1994 -- or, come to that, see Aristotle, or Hume, or almost any pre-twentieth century cognitive theorist). 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 (Thomas, 1998, 1999). As Coleridge (1817) 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 (and, probably, vice-versa)

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..

The concept of consciousness appears to have had little currency before the 17th century. Not only did philosophers before Descartes fail to worry about how consciousness fitted into the natural world, they did not even claim to be conscious. If we are conscious, however, we must assume that they were too, and it hardly seems plausible that they could have been unaware of it. In fact, when the mind was discussed in former ages, both before and within the work of Descartes, the concept of imagination filled most (not all) of the key conceptual roles that consciousness fills today. Although it was not considered uniquely problematic, in the way that consciousness is, imagination continued to be used in these ways long after the Cartesian revolution. It was both the mental arena where thinking took place - where ideas (images) had their being and their interaction - and, implicitly, the power whereby the deliverances of the material sense organs were integrated and rendered meaningful (and, thereby, rendered 'mental'). This suggests that the study of the imagination (in the relevant senses) ought to have a considerable bearing on the study of consciousness, and it may even provide a way to outflank the notorious 'hard problem' that seems to stand in the way of a direct scientific assault on consciousness itself.

Can theories of mental imagery, conscious mental contents, developed within cognitive science throw light on the obscure (but culturally very significant) concept of imagination? Three extant views of mental imagery are considered: quasi‐pictorial, description, and perceptual activity theories. The first two face serious theoretical and empirical difficulties. The third is (for historically contingent reasons) little known, theoretically underdeveloped, and empirically untried, but has real explanatory potential. It rejects the “traditional” symbolic computational view of mental contents, but is compatible with recentsituated cognition and active visionapproaches in robotics. This theory is developed and elucidated. Three related key aspects of imagination (non‐discursiveness, creativity, and seeing as) raise difficulties for the other theories. Perceptual activity theory presents imagery as non‐discursive and relates it closely to seeing as. It is thus well placed to be the basis for a general theory of imagination and its role in creative thought.

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

The principal temptation toward substance dualisms, or otherwise incorporating a question begging homunculus into our psychologies, arises not from the problem of consciousness in general, nor from the problem of intentionality, but from the question of our awareness and understanding of our own mental contents, and the control of the deliberate, conscious thinking in which we employ them. Dennett has called this "Hume's problem". Cognitivist philosophers have generally either denied the experiential reality of thought, as did the Behaviorists, or have taken an implicitly epiphenomenalist stance, a form of dualism. Some sort of mental duality may indeed be required to meet this problem, but not one that is metaphysical or question begging. I argue that it can be solved in the light of Paivio's "Dual Coding" theory of mental representation. This theory, which is strikingly simple and intuitive (perhaps too much so to have caught the imagination of philosophers) has demonstrated impressive empirical power and scope. It posits two distinct systems of potentially conscious representations in the human mind: mental imagery and verbal representation (which is not to be confused with 'propositional' or "mentalese" representation). I defend, on conceptual grounds, Paivio's assertion of precisely two codes against interpretations which would either multiply image codes to match sense modes, or collapse the two, admittedly interacting, systems into one. On this basis I argue that the inference that a conscious agent would be needed to read such mental representations and to manipulate them in the light of their contents can be pre-empted by an account of how the two systems interact, each registering, affecting and being affected by developing associative processes within the other

The term schema (plural: schemata, or sometimes schemas) is widely used in cognitive psychology and the cognitive sciences generally to designate "psychological constructs that are postulated to account for the molar forms of human generic knowledge" (Brewer, 1999). The vagueness of this definition is no accident (and no sort of failing on Brewer's part). In fact schema is used in such very different ways by different cognitive theorists that the term has become quite notorious for its ambiguity (Miller, Polson, & Kintsch, 1984 p. 6). However, a concept of..

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