I want to discuss 2 strategies I see used by advocates of materialism when trying to counter the devastating objection that materialism cannot account for the existence of first-person phenomenal experience. Both of the strategies make an insightful point, but then overstate the traction of this point on the essential problem thereby showing the materialists don’t really "get" the problem.
The first strategy is to improve upon the traditional materialist argument that experiential states are necessarily identical to brain states (“internalist materialism”). Rather, we should identify the contents of experience with external happenings. Here, brain states represent contents which themselves are external to the body (e.g. the impact of light waves on the surface of the apple). I just saw a reference to this strategy in this review of Gregg Rosenberg’s book by Paul Skokowski. Skokowski misses the point. Arguing that (at least some of) the contents of consciousness (“qualia”) are outside the cranium is a good idea, but experience itself is not thereby reduced to a material explanation. First off, I still believe the contents have a qualitative character which resists reduction; but perhaps more importantly, qualia are only one aspect of the 2-sided nature of experience itself: phenomenal contents exist only in order to be subjectively experienced. As Rosenberg explains better than I can here, experience is a process which by its nature has inseparable dual aspects of an experiencer as well as the experienced. Even if you could reduce one aspect of the process (qualia) to the physical, you cannot reduce both aspects of the process to the physical without effectively eliminating experience from your world-model altogether. Now, to repeat my point from above, I do think the externalist concept of qualia is an important insight to consider. The best description of this I have read is from Max Velmans, whose book Understanding Consciousness I recommend. Because Velmans truly understands the issues here, however, he is not a materialist.
The second strategy is most famously included in Daniel Dennett’s Consciousness Explained. It is a straw man argument which tries to show that the experiencer doesn’t exist. It proceeds by first arguing that the common sense notion of our first-person experience requires the existence of a homunculus which is the observer of qualia (thus breaking into distinct parts what really is an intrinsically dual-aspect process). Then it proceeds to show that our everyday idea of the self (which is like a homunculus) is an illusory concept. Here, the valid insight is that our reflective, introspective sense of self is a fragile and flawed construct which is at least one step removed from experience itself. Many studies show the “self” to be less unified and robust than we tend to think, and Libet’s experiments even put into question whether this self-construct has the ability to impact our actions! But while careful phenomenology will concur that the reflective (deliberative, introspective) self is a psychological construct of sorts (see for instance this post), it has as its precedent and its foundation real and unmediated first-person experience. So the argument that our naïve idea of self is a flawed concept has no impact on the reality of experience itself.
Note on Terminology: I’ve been noticing that both advocates and critics are returning to the use of the term “materialism” rather than “physicalism” to label the position. The idea is that even though we know that the word “material” is unable to do justice to the nature of the phenomena described by present day physics, materialism seems an easier and less obscure term compared to physicalism. BTW, while the incidence of this may be declining, I continue to emphasize that it is a mistake to conflate materialism with naturalism. Naturalism is a broader term which includes materialism as a sub-theory but can also encompass theories which expand upon the entities and/or processes of physics without invoking traditionally “supernatural” entities or processes such as mind/spirit substances or ad hoc divine interventions.