Hume contributed to the theory of ideas by distinguishing impressions from ideas. This refinement of Locke's theory is usually held to be a clarification of Locke's broad use of the term ‘idea,’ and yet the distinction has remained problematic. The bifurcation of the Lockean realm of ideas necessitated an explanation of the relations between the newly named entities. The most basic aspects of this relationship, as presented in the Treatise, are that impressions cause ideas and that ideas represent impressions. In this paper I will argue that Hume's theory cannot accommodate the claim that impressions cause ideas, and that this fundamental inability to trace the causal history of an idea is the source of several other problems in Hume's philosophy of mind.

Reid defended common sense against scepticism by appeal to the claim that our faculties should be considered trustworthy until some argument proves them to be untrustworthy. He believed, of course, that no such argument would be forthcoming. In this paper, we shall investigate Reid's defense of the faculty of perception and the evidence of the senses by analogy with the faculty of language and the evidence of testimony. Reid argued that the evidence of testimony should be trusted unless there is reason to think it untrustworthy and by analogy, that the evidence of the senses should be trusted unless there is reason to think it untrustworthy. He admitted the fallibility of such evidence but contended that such fallibility is characteristic of all our faculties. Moreover, and perhaps most important, Reid developed a psychological theory of the faculties of perception and language that showed the analogy between these two faculties to be very exact indeed.

Recent functionalist accounts of the mental, at least on the part of philosophers, have often been a result of dissatisfaction with the reductionist accounts championed by such physicalists as Place, Smart and Feigl. In particular this new account gained momentum from the growing belief that our map of the mental, at least in regard to the higher cognitive functions, does not seem to be a map of the brain and its processes. The more we find out about the working brain, the less we are able to cling to the belief that our talk about beliefs, evaluations, intentions, desires and motives gives us information about the structure or functioning of our brains.

In recent years, functionalism has emerged as the most appealing candidate for a materialistic theory of mind. Its central thesis - that types of mental states can be defined in terms of their causal and counterfactual relations to the sensory stimulations, other internal states, and behavior of the entities that have them - offers hope for a reasonable materialism: it promises type-identity conditions for beliefs, sensations, and emotions that are not irreducibly mental, yet would permit entities that are physically quite different to be in mental states of the same type.

I‘m a materialist, and not too embarassed about it. It would be nice to have a knock down argument to defend materialism, but not having one, I instinctively fight off idealists, dualists, skeptics, or whatever, with the same punches and feints used by materialists from time immemorial. Like, say, the snide observation that a material like liquor gets even my idealist friends drunk, or that the senile dualists I have known don't seem at all to consist of ageless minds trapped in aging bodies. I will not resort to ad baculum, because all non-materialists I‘ve known, of whatever stripe, act as though tampering with their bodies is the same as tampering with their very selves.

One way to judge whether sensations are merely part of the causal order and not part of the cognitive or epistemic order is to determine whether or not sensations control to any extent the meaning of our observation terms. Should our observation terms have their meanings even in part determined by sensations then this would seem to be evidence that sensations are of the cognitive order. In a recent and noteworthy book, Scientific Realism and the Plasticity of Mind, Paul Churchland offers a development of the Sellarsian idea that sensations play a merely causal role in perception. Churchland also cites Paul Feyerabend, whose adaptation of the Sellarsian position he finds more to his purpose. The central argument of Churchland's book and the one which will be most particularly dealt with herein is an attempt to show that facts about sensations are totally irrelevant to the meaning of observation terms, even to the meaning of common observation terms such as 'hot,' 'cold,' 'white,' and 'black.' It is Churchland's contention, then, that facts about the intrinsic nature of sensations (as opposed to facts about their roles in causal chains) are semantically irrelevant.

I must begin by thanking the editors for offering me the opportunity to respond to two of the other papers in this collection: ‘A Materialist's Misgivings about Eliminative Materialism,’ by Jeff Foss; and ‘Sensation, Theory, and Meaning,’ by Bonnie Thurston and Sam Coval. In some earlier publications I have defended eliminative materialism at some length (1981, 1984), and in others I have argued that the semantics of common observation terms is exhausted by their inferential or conceptual role, to the exclusion of any purely phenomenological component (1975, 1979). Foss criticizes the first thesis; Thurston and Coval, the second. I propose to defend both.

Imagination works upon desires and needs in a variety of ways. Different sensibilities will concentrate upon different of its operations and neglect - or even ignore - others. Thus Rousseau (and in some ways Plato, as we shall see) takes a very gloomy view of the uses of imagination. He sees only its dark aspect, under which it is a prime source of wretchedness:

Is amnesia the mother of discontinuity? Perhaps surprisingly, amnesia is perfectly compatible with psychological continuity. Think, for example, of David Wiggins’ version of Locke. Wiggins first describes a relation C of strong co-consciousness which gives continuity ‘between person Ptj and person Qtk such that, for some sufficiency of things actually done, witnessed, experienced, … at any time by Ptj, Qtk should later have sufficient real or apparent recollection of then doing, witnessing, experiencing, … them.’ Wiggins continues: