The Hard Problem of Consciousness, as defined by Chalmers, holds such sway in the study of consciousness that it is often taken as synonym for “the problem of consciousness”, at least for that really interesting kind of consciousness: phenomenal consciousness. Chalmers has not been alone in advocating the view that consciousness poses a special kind of problem, distinct and more challenging than other problems in the study of the mind. Nor has he been alone in arguing that the nature of consciousness poses a challenge to the materialistic view of world. Prior to Chalmers work, Nagel’s (1974) worries about taking an objective stance on something inherently subjective and Levine’s (1983) concerns about there being an explanatory gap between material accounts of the brain and phenomenology expressed similar concerns, to name just two of the of the many prominent philosophers who took such a view in the second half of the twentieth century. The idea that consciousness has a different nature to the rest of the world, of course, has a much longer history in philosophy. Yet, in contemporary philosophy, and indeed in other disciplines studying consciousness, Chalmers’ presentation seems to hold a special appeal and power in setting up the problem of consciousness.

Yet, since Chalmers’ initial publications presenting consciousness as posing a special Hard Problem, his characterisation has been widely criticised. Many philosophers of no-lesser status and influence than Chalmers, e.g. Churchland (1996) and Dennett (1996), argued that Chalmers was just wrong in his characterisation of the problem of consciousness (let alone any purported solution). Many of us seemed to have agreed that Chalmers doesn’t get the problem of consciousness right when he describes it as Hard, but nothing like a consensus has been reached.

In this special issue we bring together a range of contemporary views on whether or not consciousness poses a Hard Problem as described by Chalmers. Many of our contributors (although not all, of course) have come to the study of consciousness only after the deadlock of the 1990s was firmly entrenched. The contributors here cover a wide range of perspectives. Some agree strongly with Chalmers’ early critics that the Hard Problem is poorly formulated and not supported by (non-question begging) argument. At the other extreme we have defences of Chalmers’ characterisation from those who take it that the Hard Problem is well formulated and that various materialist solutions to the problem fail. We commend these to the readership with limited optimism that we might move on from the deadlock created by the Hard Problem.

Robinson offers a partial defence of the Hard Problem by arguing that a proposed materialist solution to the problem fails. He argues that Pettit and more recently Clark’s “looks as powers” approach to looking red can’t work because the physical property which has the (supposed) power to look red is complex in a way that is not evident in the experience itself. This means that they cannot be used, as had been intended, to solve the Hard Problem of consciousness.

McClelland considers the explanatory targets of a theory of consciousness and concludes that the problem is neither Hard, nor easy, but “tricky”. He does this by distinguishing two separate questions: the “consciousness question” and the “character question”. The first concerns whether there is something it is like for a subject, the second is what it is like for the subject. The zombie thought experiment raises problems for the consciousness question whereas the inverted spectrum thought experiment raises problems for the character question. McClelland suggests these two problems are independent such that one may be deemed Hard while the other may be easy. As such there could be stable middle ground for those who aren’t attracted to either the claim that consciousness is Hard or the claim that it is easy.

Related distinctions between qualia and the appearance of qualia to the subject play a role in two other papers. First, Sebastian examines the Kripkean intuition (1972) [which can also be found in Nagel (1974)] that an appearance reality distinction cannot be drawn for consciousness. The goal is to make room for a gap between the primary and secondary intensions of phenomenal statements such that an a posteriori identity, along the lines of that of water with H20 is made possible. This is because, as Block (1995) has argued, our cognitive access to our experiences is independent of their phenomenal qualities. Sebastian argues that evidence for this dissociation can be found in Sperling’s (1960) classic partial report experiments and in imaging evidence that suggests a dissociation between areas involved in cognitive access and those that are active when the subject is dreaming. The upshot is, that because the cognitive access mechanism via which we know our experiences is dissociable from the experiences themselves, we can get the separation between primary and secondary intensions that is required for an identity.

Second, Nessier considers the nature of subjectivity and argues that, despite its appeal, subjective thought is not best understood as inner awareness. As such, the problem of subjectivity can be separated from the problem of phenomenal properties or qualia. He argues that problems arise when we think that qualia contain within themselves not only a qualitative nature, but also an awareness of this nature, such that they are both the object and the means of knowing. As representation involves (at least) two things—the vehicle (the thing that is doing the representing) and the object (the thing that is represented)—this “paradoxical duality” seems to undermine a representational account of knowledge for qualia. It also opens the door to the claim that our knowledge of qualia is infallible—if the instantiation of the quale includes an awareness of it, then we cannot be wrong about the nature of our experiences. Nessier argues that this is mistaken because we have confused infallibility with incorrigibility. It is not that I cannot be wrong about my experiences, but rather, because my experiences are not accessible to anyone but myself, I cannot be corrected by others. The upshot is that whatever problems arise from the phenomenal nature of qualia, they are not accompanied by problems due to their subjectivity.

Following this we have a series of three papers that argue that the notion of a Hard Problem begs the question against materialist accounts of consciousness or different characterisations of the problem of consciousness.

Ritchie builds on Perry’s (self-acknowledged) failed attempt to show that the zombie argument is circular because it assumes epiphenomenalism. He argues that it is circular because it assumes causal theses that the physicalist would reject. By considering one of the best arguments for physicalism, namely the “causal argument” that many apparent effects of phenomenal experiences have full physical causes and so to avoid causal overdetermination, phenomenal experiences must be physical causes, Ritchie argues that the physicalist is committed to three causal theses. Namely; closure (all physical effects have physical causes); no overdetermination and; efficacy (all phenomenal states cause physical events). The difficulty for the proponent of the Hard Problem is that these causal theses mean that the phenomenal must supervene on the physical and therefore that zombies are (ideally) inconceivable. What this shows is that zombies are only possible if one of the causal theses that are entailed by physicalism are false. That is, one cannot use the conceivability of zombies as an argument against physicalism because zombies are only possible if one of the causal theses entailed by physicalism, and therefore physicalism itself, is false.

Schier and Carruthers are also concerned about circularity in the arguments for a Hard Problem of consciousness. Their goal is to examine the arguments put forward for the existence of the “hard phenomenon” i.e. that which is inexplicable in structural or functional terms and therefore that which leaves us stuck with the Hard Problem. They quickly uncover that all that is offered is the claim that it is self-evident that there is a hard phenomenon. While every theory needs to start somewhere, taking the existence of the hard phenomenon as axiomatic in the face of scepticism about its existence means that his criticisms of those who reject such an axiom are impotent. They go on to show that although Chalmers’ does not use them in this way, the intuitions that are employed in dualistic thought experiments cannot be used as evidence for the existence of the hard phenomenon. This is for the simple reason that the intuitions are only true if there is a hard phenomenon. Their take-home point is a warning to those who are interested in using the intuitions as tools in theory building or as catalysts for conceptual change: don’t let your interest in the dualist’s intuitions trick you into accepting their characterisation of the phenomenon to be explained.

Piccinni argues that thanks to a failure to pay attention to the accessibility relations between possible worlds we have missed that the zombie conceivability argument begs the question. To evaluate the truth of a modal statement (such as ‘zombies are possible’) at a world, w, we need to consider the truth value of the statement at possible worlds which are accessible from that world. Failure to consider accessibility relations can lead to contradictions. But, in order to consider whether two worlds are accessible we need to know the relevant facts. It is not until we know that ‘P’ is necessarily true at w that we can say that w’ where ‘P’ is false must be inaccessible from w. So the question becomes: what must be true about our world for zombie worlds to be accessible? The problem for the proponent of the Hard Problem is that if physicalism is true at our world and phenomenal properties supervenes on physical properties, then zombie-worlds are not accessible. That is, the zombie argument against physicalism begs the question. Piccinni goes on to consider why such little attention has been paid to this circularity and suggests that it is because the accessibility of zombie worlds is built into the standard “Horganic” conception of physicalism. At the heart of Horganic physicalism is the claim that any minimal physical duplicate of our world is a duplicate simpliciter. But, this means that zombie worlds, which are minimal physical duplicates of our world, are accessible from our world and therefore relevant to establishing the truth of physicalism. Piccinni concludes that Horganic physicalism makes phenomenal physicalism necessarily false. Clearly something has gone awry. By constructing a zombie argument against property dualism Piccinni argues the problem is with conceivability arguments themselves. He takes this to be evidence that the method of consulting one’s a priori intuitions about conceivability and possibility will not be able to resolve this issue because the methods used are not publically accessible. If we have different intuitions we just have to agree to disagree. The upshot is that conceivability arguments will never be conclusive and so we should use other methods instead.

Irvine takes up the argument where the previous three papers finished. She takes the years of disagreement and stalemate to be evidence that the intuition game cannot be resolved and instead embarks on a Quinean process of doing the science to see whether the conceptual deadlock can be resolved by conceptual change. This is a fruitful approach, because, as Irvine argues, the data already calls into question our pre-theoretical notion of consciousness that figures so prominently in the thought experiments. In particular it seems that there is no clear answer to the question: did you experience something or not? The answer depends on when and how you measure experience such that the claim that there is a phenomenon that deserves to be called ‘consciousness’ is called into question. The upshot is that perhaps the reason why consciousness remains scientifically inexplicable is not that it is inherently mysterious, but because it does not exist. Importantly, Irvine does not deny that we have experiences, rather she argues that what we call ‘experiences’ are a range of diverse cognitive phenomenon that form an arbitrary group for which we should not expect a unified explanation.

Finally we close with two papers that offer other grounds for thinking that the Hard Problem offers only a pseudo-problem for consciousness studies.

Pauen argues that for the zombie and inverted spectrum thought experiments to work consciousness must be epiphenomenal. He does this by introducing the notion of part-time Zombies and inverts, namely creatures that switch between being zombies and not zombies or inverts and not inverts. The crucial point is that this switch is functionally indiscernible, even for the part-time zombie or invert. For the part-time zombie to be able to tell that it had switched from its zombie to its non-zombie state it needs to be able to reliably recognise at least some phenomenal differences. But, for such a recognition to occur there would need to be a change in the zombie’s beliefs (even if only their first-person beliefs) and so there would be a functional difference. Zombies and inverts undermine the possibility of any first-person authority regarding our experiences and so undermine the qualiophile’s claim that to deny the existence of phenomenal qualities which are functionally inexplicable is to deny the obvious. If they are functionally inexplicable then how can they make the functional difference required for us to have knowledge of them in the first place?

Kostic argues that the Hard Problem’s scope is much more limited than many think. Whilst standardly the Hard Problem is taken to be a metaphysical problem, Kostic argues that it is merely an epistemic problem. In particular, it is a problem of knowing how concepts which refer to phenomenal properties and concepts which refer to brain states can be co-referential. This, he argues, is distinct from knowing why brain processes have phenomenal properties. The upshot is that a failure to relate the concepts is not a bar to the ability to give a scientific explanation of phenomenal qualities.

The diversity of approaches exemplified in this special issue make it clear that, despite our continued hope, a resolution to the debate will remain elusive. But we are confident that these contributions will help to de-populate Chalmers’ side of the great divide, if not by migration across it, than by removal of the divide itself.