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Yujin Nagasawa has recently defended Frank Jackson’s knowledge argument from the “inconsistency objection.” The objection claims that the premises of the knowledge argument are inconsistent with qualia epiphenomenalism. Nagasawa defends Jackson by showing that the objection mistakenly assumes a causal theory of phenomenal knowledge. I argue that although this defense might succeed against two versions of the inconsistency objection, mine is unaffected by Nagasawa’s argument, in which case the inconsistency in the knowledge argument remains.

Frank Jackson's knowledge argument against physicalism has caused an extensive debate. In this paper, I sketch and examine a new argument against Jackson's view, an argument which appears to retain more of physicalism than other replies to Jackson. this argument draws strength from a causal theory of knowledge, and hold that there is no knowledge of epiphenomenal qualia, hence that Jackson's main conclusions from the thought experiment are incorrect. There are still problems with this argument, however, so the question remains how much of the mental that can be accounted for in physicalist terms.

Frank Jackson has abandoned his famous knowledge argument, and has explained why in a brief "Postscript on Qualia" (1998). This explanation consists of a direct argument, and an attempt to explain away the intuition that lies at the heart of the knowledge argument. The direct argument is clarified and found to be subtly question-begging. The attempt to explain away the key intuition is reviewed and found to be inadequate. False memory traces, which Jackson mentions at the beginning of the direct argument, are discussed and found not to materially affect the force of the knowledge argument.

According to representationalism, the qualitative character of our phenomenal mental states supervenes on the intentional content of such states. Strong representationalism makes a further claim: the qualitative character of our phenomenal mental states _consists in_ the intentional content of such states. Although strong representationalism has greatly increased in popularity over the last decade, I find the view deeply implausible. In what follows, I will attempt to argue against strong representationalism by a two-step argument. First, I suggest that strong representationalism must be _unrestricted_ in order to serve as an adequate theory of qualia, i.e., it must apply to all qualitative mental states. Second, I present considerations to show that an unrestricted form of strong representationalism is problematic.

Frank Jackson argued, in an astronomically frequently cited paper on 'Epiphenomenal qualia'[Jackson 1982 that materialism must be mistaken. His argument is called the knowledge argument. Over the years since he published that paper, he gradually came to the conviction that the conclusion of the knowledge argument must be mistaken. Yet he long remained totally unconvinced by any of the very numerous published attempts to explain where his knowledge argument had gone astray. Eventually, Jackson did publish a diagnosis of the reasons why, he now thinks, his knowledge argument against materialism fails to prove the falsity of materialism [Jackson 2005. He argues that you can block the knowledge argument against materialism - but only if you tie yourself to a dubious doctrine called representationalism. We argue that the knowledge argument fails as a refutation of either representational or nonrepresentational materialism. It does, however, furnish both materialists and dualists with a successful argument for the existence of distinctively first-person modes of acquaintance with mental states. Jackson's argument does not refute materialism: but it does bring to the surface significant features of thought and experience, which many dualists have sensed, and most materialists have missed.

The knowledge argument aims to refute physicalism, the view that the world is entirely physical. The argument first establishes the existence of facts (or truths or information) about consciousness that are not a priori deducible from the complete physical truth, and then infers the falsity of physicalism from this lack of deducibility. Frank Jackson (1982, 1986) gave the argument its classic formulation. But now he rejects the argument (Jackson 1998b, 2003, chapter 3 of this volume). On his view, it relies on a false conception of sensory experience, which should be replaced with representationalism (also known as intentionalism), the view that phenomenal states are just representational states. And he argues that mental representation is physically explicable.

1. Introduction In ‘The Refutation of Idealism’, G.E.Moore observed that, "when we try to introspect the sensation of blue, all we can see is the blue: the other element is as if it were diaphanous" (1922; p.25). Many philosophers, but Gilbert Harman (1990, 1996) in particular, have suggested that this observation forms the basis of an argument against qualia, usually called the argument from diaphanousness or transparency.1 But even its friends concede that it is none too clear what the argument from diaphanousness—as I will call it—is (Tye 2000; p.45).2 The purpose of this paper is to formulate the argument, and to assess its merits. My conclusion will be that qualia realists have little to fear from the argument—provided both qualia and diaphanousness are properly understood.