‘[F]undamentally an organism has conscious mental states if and only if there is something that it is like to be that organism — something it is like for the organism.’

So writes Thomas Nagel in his famous 1974 paper ‘What is it like to be a bat?’ (p.436). It is a compelling thought and one that seems self-evidently true. (I remember coming up with the same idea when I was a teenager and thinking it a great insight, and I’m sure many others have had the same experience.) But is Nagel’s claim correct or might it be seductively wrong? It depends, I think, on how we interpret it. Here are two things it might mean.

The first is that having conscious experiences involves having a certain kind of introspective self-awareness — an awareness of one’s own mental responses to the world. For you to be conscious is for you to know what you are like as you respond to the world, as well as what the world is like as it affects you. I’ll call this introspective subjectivity. Introspective subjectivity, we might say, stresses the ‘like’ part of ‘what it is like to be’.

The second thing Nagel might mean is that to have conscious experiences is to have a form of immediate inner awareness that exists simply in virtue of being the thing one is and that is not dependent upon introspective mechanisms. I’ll call this intrinsic subjectivity. We might say that this stresses the ‘be’ part of ‘what it is like to be’.

These two kinds of subjectivity are very different. Introspective subjectivity is not essentially private. With the right apparatus, another person might monitor the same internal states my introspective mechanisms do and so share my introspective awareness. But intrinsic subjectivity cannot be shared. The only way someone could share what it’s like to be me in the intrinsic sense is to be me, or perhaps a duplicate of me.

Now there doesn’t seem to be any special difficulty in understanding how a creature could possess introspective subjectivity. it would just need to have suitable introspective mechanisms targeting its own internal responses and hooked up in the right way to the rest of its cognitive system. But intrinsic subjectivity looks like a complete mystery. How does this inner awareness arise? What exactly is the subject of it? Which things have it? What does it do? How can we even investigate it? These look like, well, hard problems.

In the literature on consciousness these two kinds of subjectivity aren’t always clearly distinguished. Some theories — most obviously panpsychist ones — are plainly theories of intrinsic subjectivity. If there is something it is like to be a rock, it’s not because the rock is capable of introspection. But other theories look like theories of introspective subjectivity. Higher-order representational theories, for example, attempt to explain consciousness in terms of the internal monitoring of experience. Yet these theories are often discussed as if they were alternative accounts of the same thing.

Nagel’s claim has become the standard starting point for theories of consciousness, but it doesn’t identify a unique explanandum and it has sent researchers off down very different paths. In my view, it is immensely plausible to think that conscious experience involves introspective subjectivity, and developing theories of introspective subjectivity should be a major research programme for cognitive science. But the pursuit of theories of intrinsic subjectivity is, I fear, misguided and futile.

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Assume for the sake of argument that (1) qualia are real and nonphysical, (2) the physical world is closed under causation (and there’s no overdetermination), and (3) apart from qualia, the mind is physical.

Now, you have experiences with qualia. But this isn’t all. You are also aware of having qualia. You can attend to your them, think about them, recall them, and respond to them. And since (given our assumptions) the qualia themselves don’t have any causal effects on you, this suggests that you have representations of your qualia. You represent your experiences as having qualia, and these representations do the causal work. Your awareness of your qualia and your responses to them are mediated by qualia representations. (I assume these are fine-grained analogue representations of some kind. You can detect and respond to changes in your qualia that you can’t conceptualize.) The representations aren’t actually caused by the qualia, of course, any more than the other effects are. They are physical states of your brain and are caused by prior brain events, but things are somehow set up so that they track your qualia perfectly.

Now consider your zombie twin – an exact duplicate of you minus the qualia. Since it is a physical copy of you, this creature will have the same qualia representations you do, and these representations will have the same effects on it as yours do on you. Call this creature a Q-zombie.

Next consider another type of zombie. This one is a physical and phenomenal duplicate of you, except for the qualia representations. It has the same qualia you do, but no representations of them; the brain circuits involved have been fried. Call this creature an R-zombie (for Representational zombie).

The Q-zombie will take itself to have qualia just like yours, and it will display the same qualia-related sensitivities, thoughts, and responses you do. It will have the same reactions to pain and pleasure, the same sensitivity to colours, sounds, and smells, and the same beliefs about the character of its conscious experiences, even though it has no qualia at all.

The R-zombie, on the other hand, will behave – well, like a zombie. The absence of qualia representations will have drastic consequences for its mental life and behaviour. It will not attend to its qualia, or think about them, or respond to them. It will exhibit various ‘blindsighted’ behaviours, reacting unconsciously to external stimuli, but it will show no sign of having conscious experiences and no awareness of pain, pleasure, colour, smell, or any other phenomenal property — even though it does in fact have exactly the same qualia you do.

Now here’s the punchline. Something really unpleasant is going to happen to you – something that will cause a lot of pain (and pain representations). There is an anaesthetic on offer, however. In fact, there are two drugs available: blue pills and red pills. A blue pill will turn you temporarily into a Q-zombie and a red pill will turn you temporarily into an R-zombie.

Which pill would you take? And would you have any trouble deciding?

Image credit: Red Pill or Blue Pill? by Tomaž Štolfa