As a philosophical expert on theories of consciousness, I try to keep abreast of the most promising recent theories. I also sometimes receive unsolicited emails from scholars who have developed a theory that they believe deserves attention. It's fun to see the latest cleverness, and it's my job to do so, but I always know in advance that I won't be convinced.
I'd like to hope that it's not just that I'm a dogmatic skeptic about general theories of consciousness. In "The Crazyist Metaphysics of Mind", I argue that our epistemic tools for evaluating general theories of consciousness are, for the foreseeable future, too flimsy for the task, since all evaluations of such theories must be grounded in some combination of dubious (typically question-begging) scientific theory, dubious commonsense judgment (shaped by our limited social and evolutionary history), and broad criteria of general theoretical virtue like simplicity or elegance (typically indecisive among theories that are live competitors).
Today, let me try another angle. Ultimately, it's a version of my question-beggingness complaint, but more specific.
Premise 1: There is no currently available decisive argument against panpsychism, the view that everything is conscious, even very simple things, like solitary hydrogen ions in deep space. Panpsychism is, of course, bizarrely contrary to common sense, but (as I also argue in The Crazyist Metaphysics of Mind) all well-developed general theories of consciousness will have some features that are bizarrely contrary to common sense, so although violation of common sense is a cost that creates an explanatory burden, it is not an insurmountable theory-defeater. Among prominent researchers who defend panpsychism or at least treat seriously a view in the neighborhood of panpsychism are Giulio Tononi, David Chalmers, Galen Strawson, and Philip Goff.
There are at least three reasons to take panpsychism seriously. (1.) If, as some have argued, consciousness is a fundamental feature of the world, or a property not reducible to other properties, it would be unsurprising if such a feature were approximately as widespread as other fundamental features such as mass and charge. (2.) Considering the complexity of our experience (e.g., our visual experience) and the plausibly similar complexity of the experience of other organisms with sophisticated sensory systems, one might find oneself on a slippery slope toward thinking that the least complex experience would be possessed by very simple entities indeed (see Chalmers 1996, p 293-7, for a nice exposition of this argument). (3.) Despite my qualms about Integrated Information Theory, there's an attractive theoretical elegance to the idea that consciousness arises from the integration of information, and thus that very simple systems that integrate just a tiny bit of information will correspondingly have just a tiny bit of consciousness.
Premise 2: There is no currently available decisive argument against theories of consciousness that require sophisticated self-representation of the sort that is likely to be absent from entities that lack theories of mind. On extreme versions of this view, even dogs and infants might not have conscious experience. (Again, highly contrary to common sense, but!) Among prominent researchers who have taken such a view seriously are Daniel Dennett and Peter Carruthers (though recently Carruthers has suggested that there might be no fact of the matter about the phenomenal consciousness, or not, of non-human animals).
There are at least three reasons to take seriously such a restrictive view of consciousness: (1.) If one wants to exit the slippery slope to panpsychism, one possibly attractive place to do so is at the gap between creatures who are capable of explicitly representing their own mental states and those that cannot do so. (2.) Consciousness, as was noted by Franz Brentano (and recently emphasized by David Rosenthal, Uriah Kriegel, and others), might plausibly always involve some sort of self-awareness of the fact that one is conscious -- apparently a moderately sophisticated self-representational capacity of some sort. (3.) There's a theoretical elegance to self-representational theories of consciousness. If consciousness doesn't just always arise when information is integrated in a system, an attractive explanation of what else is needed is some sort of sophisticated ability of a system to represent its own representational states.
Now you might understandably think that either panpsychism or a human-only views of consciousness is so extreme that we can be epistemically justified in confidently rejecting one or the other. If so, we can run the argument with weaker versions of Premise 1 and/or Premise 2:
Premise 1a (weaker): There is no currently available decisive argument against theories of consciousness that treat consciousness as very widespread, including perhaps in organisms with fairly small and simple brains, or in some near-future AI systems.
Premise 2a (weaker): There is no currently available decisive argument against theories of consciousness that treat consciousness as narrowly restricted to a class of fairly sophisticated entities, perhaps only mammals and birds and similar organisms capable of complex, flexible learning, and no AI systems in the foreseeable future.
Premise 3: All general theories of consciousness commit to the falsity of either Premise 1, Premise 2, or both (alternatively Premise 1a, Premise 2a, or both). If they do not so commit, then they aren't general theories of consciousness, though they may of course be perfectly fine narrow theories of consciousness, e.g., theories of consciousness as it happens to arise in human beings. (I've got a parallel argument against general theories of consciousness even as they apply just to human beings, based on considerations from Schwitzgebel 2011, ch. 6, but not today.)
Therefore, all general theories of consciousness commit to the falsity of some view against which there is no currently available decisive argument. They thereby commit beyond the evidence. They must either assume, or accept on only indecisive evidence, either the falsity of panpsychism, or the falsity of sophisticated self-representational views of consciousness, or both. In other words, they inevitably beg the question against, or at best indecisively argue against, some views we cannot yet justifiably reject.
Still, go ahead and build your theory of consciousness. You might even succeed in building the true theory of consciousness, if it isn't yet out there! Science and philosophy needs bold theoretical adventurers. But if a skeptic on the sidelines remains unconvinced, thinking that you have not convincingly dispatched some possible alternative approaches, the skeptic will probably be right.
ETA: In order to constitute an argument against a candidate theory, as opposed to merely an objection to such theories, perhaps I need to put some weight on the positive arguments in favor of views of consciousness that conflict with the theory being defended. Thanks to David Chalmers and Francois Kammerer on Facebook for pushing me on this point.