The respective ideas of Hume, Wittgenstein and Mahayana Buddhists are interrelated and are characterized by empiricism and naturalism. Not surprisingly the response they invite most prominently is a Kantian one. But Kant deduced that there had to be necessary preconditions for the possibility of representational experience: it was the representation of the world that had to be “conditioned.” None of these thinkers – not even Hume on my reading – defines experience as involving the formation of representations in the first place. Furthermore remember that the subject of this chapter is consciousness, and consciousness is not obviously amenable to a representational “explanation” even for those who are inclined to address intentionality that way. In any event if one balks at, say, the “solipsism” argument I certainly agree that it is a bit breath-taking, but I wouldn’t introduce it here if I knew of an argument that refuted it.
The present set of arguments, that will now be deployed against the “absent qualia” arguments that purport to show that there is a metaphysical problem about phenomenal properties, can all be attributed to some combination of Hume, Wittgenstein and/or Buddhism. The first two arguments are “soft”: they start with two respective points about the nature of language and conclude that private qualitative experience, whatever its ultimate ontological status may be, cannot be the subject of language. This is a soft conclusion because it sets aside the question of whether there really is anything that can coherently be regarded as “inner,” private experience. The remaining arguments are “hard”: they start with the inseparability of mind, experience and world and conclude that it is incoherent to posit the existence of phenomenal properties if these are taken to be mental properties distinct from the physical properties of the experienced world. However although the first two arguments are soft they do, if persuasive, suffice for the naturalization of psychology, because they demonstrate that qualitative experience, whatever that may be, could never have been a subject for natural science, and so is not a problem for natural science.
1) If language needs inter-subjective criteria of appropriate conditions of use then the phenomenal vocabulary, like all language, cannot function in virtue of referring to anything “private” to the individual. This argument is explicit in Wittgenstein, a case can be made that it is implicit in Hume’s verificationist epistemology. It is “soft”: it leaves the ontological status, if any, of qualitative experience alone. It naturalizes psychology the way that classical, early 20th century behaviorism naturalized psychology: an operationalist protocol excludes reference to the “inner” from science, so understood.
2) If the “meaning” of language/symbols is nothing more nor less than everything that has been accomplished through the use of individual, concrete tokens, then the phenomenal vocabulary cannot function by referring to anything private. This is functional-role semantics and it is unique to Wittgenstein among this group (although other philosophers, such as Pragmatists, also develop this sort of operationalist account of language). It is soft; the ontological status of qualia is not addressed directly.
3) If the self is nothing neither more nor less than the experiences of the world by the self, then there can be no duality between the “self” and the “world.” This is Wittgenstein’s “solipsism” argument, first presented at the end of the Tractatus, and the same idea is found in the Mahayana sutras of classical Buddhism and in Zen Buddhism. This is a “hard” argument: on this view the existence of phenomenal properties is denied. It is another argument that seems implicit in Hume, but Hume does give a very explicit argument to the same effect:
4) If experience defines the limit of what can be known, it is absurd to posit a distinction between the “mental” and the “physical.” Hume’s version is quite as hard as #3 because it produces the same conclusion that it makes no sense to speak of either side of the duality of mind and matter: both concepts collapse simultaneously. It is neither materialist nor idealist, but a position of non-duality. This view is shared by Berkeley.
5) Consciousness cannot be located in the world, so consciousness cannot be said to have any properties. This argument follows from #3. It is explicit (and elaborated at great length) in its Buddhist version but also clearly implicit in both Hume and Wittgenstein. It does not follow from this that consciousness cannot be a property. Just what we mean when we predicate consciousness of a thing is what is at question, although I take it as now established that the criteria for predications of consciousness are necessarily operational.
If the most tempting line of rebuttal to all of this is a Kantian one, remember that these arguments are here deployed to show that there are no phenomenal properties. This question about consciousness has been disentangled from the problem of intentionality. The motivations of the three sources of the set of arguments are varied: Hume fills out the radical implications of empiricist epistemology as far as they go; Wittgenstein has a vision about the foundations and limits of logic; and the classical Buddhists appear to take the metaphysical implications of non-duality both literally and seriously. Whatever one makes of these sources (or of my interpretations of them), it is at least fair to say that they place the burden on those who would say that there are phenomenal properties, metaphysically distinct from physical properties, to articulate reasons why anyone should think so.
However the discussion is far from over. Having assembled this set of arguments I now need to apply them to the various “absent qualia” arguments that have been the backbone of the critique of functionalism and the emergence of consciousness as a problem for cognitive science over the past thirty years.
My aim is not to show that operationalist theories such as functionalism are adequate to address the problem of consciousness; I am not “defending” functionalism from the “absent qualia” critique. My view is that intentional predicates must be handled operationally, while phenomenal predicates cannot be – that is, they cannot be to the philosopher’s satisfaction, notwithstanding the fact that all predication, to be intelligible, must adhere to intersubjective operational criteria. Functional descriptions abstract away from hardware: they include no physical descriptions. In the same way they abstract away from consciousness: they include no phenomenal descriptions. Of course this is true because there is no such thing as “phenomenal description” if by that one means reference to “private” experience. But a further point is that there is no reason to think that phenomenal experience is multiply realizable (supervenient), while intentional states are self-evidently so.
The point of the following discussions of the inverted spectrum problem and the zombie problem (both variants of the “absent qualia” problem) is not, then, to vindicate functionalism as a theory of consciousness. Theories don’t address pseudo-problems. The significance of the “absent qualia” arguments in the present context arises when they are offered as evidence that physicalism is ontologically incomplete.