Michael Tye on Vagueness about Consciousness

In late August, about two days after I finished drafting my new paper "Borderline Consciousness, When It's Neither Determinately True nor Determinately False That Consciousness Is Present", I learned that Michael Tye had a new book forthcoming on the same topic: Vagueness and the Evolution of Consciousness.

Tye is eminent in consciousness studies, and he has also written influentially about the logic of vagueness. In the past, he had defended, but not in detail, the idea that consciousness is a vague property, admitting borderline cases -- the same thesis I defend in that circulating draft paper. You know that feeling when you discover that someone much better known than you is working on the same thing you've been working on, probably with a similar view and probably a couple of steps ahead? Right. Eek!

So of course I had to read Tye's new book straightaway. I received it last week.

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Chapter 1 is surprising, given Tye's previous work defending vagueness.

First (the unsurprising part), Tye argues that consciousness is vague, that is, that there must be a range of "borderline cases" between being conscious and being non-conscious. His argument is similar to mine: If consciousness is a physical phenomenon or grounded in a physical phenomenon, it pretty much has to have fuzzy boundaries since basically all physical phenomena have fuzzy boundaries, including those normally associated with consciousness (such as having neurons or integrating a certain amount of information). Therefore, between non-conscious bacteria and conscious humans, there must be some animals who are only borderline conscious. I'd add, though it's not Tye's emphasis, that there must also be transitional, borderline states between non-conscious sleep and conscious waking.

Second (the surprising part), Tye argues that consciousness cannot be vague on the grounds that we cannot present examples of, or even conceive of, borderline cases of it. He rejects a couple of putative examples. Feeling groggy upon waking is not borderline consciousness, but rather a type of conscious experience (perhaps with indistinct contents). Also, hearing a tone fade into silence (an example he used in his own earlier work) is not a case of borderline consciousness because one can hear silence, so throughout the fading you are definitely having a conscious experience, though it might one with vague or indeterminate representational content such as "maybe there's a very quiet tone or maybe there's just silence".

Tye presents these two arguments as a "paradox". On the one hand, we seem to have a good argument that consciousness must be a vague property, admitting of borderline cases. On the other hand, we seem to have a good argument that consciousness cannot be a vague property, admitting of borderline cases. He concludes by saying, "So, consciousness, it seems, is both vague and not vague. What to do? Houston, we have a problem!" (p. 18).

Before presenting Tye's solution to that problem, let me suggest that the two arguments -- one pro-vagueness, one anti-vagueness -- are not equally strong. The first argument is approximately as strong as standard-issue (non-panpsychist) materialism. If consciousness is, or is grounded in, large, floppy, fuzzy-edged properties like having a brain of a certain sort or having cognitive capacities of a certain sort, as basically all ordinary materialist philosophers think, then barring something quite strange, consciousness too must have vague boundaries.

The anti-vagueness argument seems weaker. From the fact that we can't conceive of borderline cases, it doesn't follow that borderline cases don't exist. The problem might be (as I argue in my paper) that there's a failure or limitation in our imaginative capacities. As Tye himself says, "The concept consciousness is such that we cannot conceive of a borderline case and that is prima facie evidence that it is sharp" (p. 16, bold added). "Prima facie evidence", he says -- not conclusive evidence. Just an initial reason in favor. Shouldn't the response for the standard-issue materialist convinced by the argument of the first part just be to reject the "prima facie evidence" and look for another explanation for our conceptual failure?

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Neither Chapter 2 nor Chapter 3 are mainly about vagueness. Chapter 2 argues against a certain panpsychist way of solving the problem of Chapter 1. Chapter 3 defends Tye's famous representationalist view of consciousness against a family of objections, along the way establishing the important point that representational contents of determinately conscious experiences can be vague. It can determinately be the case, for example, that you're having a visual experience with vague, partly indeterminate contents, as when you are looking through blurry glasses at something you can't quite make out.

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In Chapter 4, Tye delivers his answer to the puzzle of Chapter 1. His answer turns on the concept of consciousness*. Consciousness* is a property

that a state must have to be conscious. Experiencing something, I propose, is a matter of undergoing an inner state (with a quasi-pictorial structure), a state that has the property of being conscious* and that also represents something. Consciousness* is not itself a representational property, nor is it a functional property.... It is, I hold, irreducible and fundamental. And it is consciousness* that is found at the level of quarks. Quarks are conscious* but not conscious (p. 79).

Concerning vagueness, Tye adds:

Consciousness* is sharp whereas consciousness essentially involves content and thus is vague. When we assert baldly that there are no possible borderline states of consciousness, we are wrong; but the borderline cases arise via the vagueness of the representational aspect of consciousness. There is no vagueness in consciousness*, the other key element of consciousness (p. 79).

I confess to finding consciousness* a bit puzzling! What is this new fundamental property? It's philosophically bold, and seemingly empirically unmotivated, to posit that quarks have not only the usual properties that particle physicists attribute to them, such as spin and "color", but also a previously unnoticed property, consciousness*, which isn't consciousness itself but which is intimately related to it. Why should we posit the existence of such a property rather than satisfying ourselves with, say, a simpler representationalism on which the only thing necessary for consciousness is having a cognitive, representational structure of a certain sort? Tye himself, in his earlier work, ranks among the chief proponents of that type of simpler representationalism about consciousness. Consciousness* is a new aspect of his view -- a change in his position (as he admits in the introduction), presumably forced upon him after long thought and dissatisfaction with his previous view.

I can see two main motivations for positing consciousness*. Both depend on treating conceivability as a compelling test of possibility.

The first is zombies. A philosophical zombie is an entity particle-for-particle identical to a person, at the finest level of functional detail, but lacking consciousness. Tye treats such zombies as conceivable and therefore possible (esp. p. 98-99). Consciousness* gives us a way to make sense of this. Zombies are microphysically like us at the finest-grain functional level, and have all the same representational contents, but their microparticles lack consciousness*. Consciousness* thus plays a role in explaining why we aren't zombies. Consciousness* is a micro-level property that we have and that zombies lack, even though every molecule in our bodies behaves outwardly in the same way (including in producing the same verbal reports of consciousness).

The second reason to posit consciousness* is more central to the vagueness project. Something about consciousness is sharp-bordered, Tye argues. But it can't be the representational content. Consciousness* thus plays the role of being this sharp-bordered property -- either present at the micro level (in us) or absent (in zombies), rather than objectionably fading gradually in as systems become bigger and more complex.

I've long found philosophers' fascination with the zombie thought experiment a little puzzling. Part of me is inclined to doubt that we can reach any substantive conclusions about the nature of consciousness by considering examples that are not even (by most zombie-theorists' own lights) physically possible.[1] Another part of me, however, is happy to concede zombie-theorists their point: Sure, there is some property we have that these hypothetical creatures would lack despite their (posited) physical-functional identity, i.e., the property of being conscious. But properties of this sort are cheap. They don't threaten materialism as a scientific hypothesis concerning what is physically possible. The zombie-business seems separable from the business of figuring out what real creatures have conscious experiences, in virtue of which physical/structural features. It is similarly separable from the business of figuring out what hypothetical but physically possible creatures would have conscious experience if we built them, in virtue of which physical/structural features.

In that concessive mood, maybe I should be fine with consciousness*. Maybe, even, it's just the thing we need to deal with the zombie case. We can then say, sure, all ordinary matter is such that if you organize it in the right way it gives rise to consciousness. All matter we can see and interact with has consciousness*, i.e., is such that it would not give rise to mere zombie fake-consciousness if you swirled it together into the form of a biological person. Hypothetically we can imagine matter that lacks consciousness*. Hypothetically we can also imagine ghosts and Cartesian souls. There's no compelling evidence that our universe contains any such things. So maybe, similarly, microparticles around here have Property NG, the property of being such that they don't require the existence of ghosts to give rise to consciousness when they are organized in the right way. Perhaps this, too, is a previously unlabeled fundamental property? Or is it maybe just the same property as consciousness*?

But let's return to vagueness. In Chapter 1, Tye argued that the fact that we cannot conceive of borderline cases of consciousness is prima facie evidence against the existence of such cases. Now, in Chapter 4, we find him -- in my view wisely -- positing the existence of borderline cases of consciousness after all, stating that it is only consciousness* that cannot be vague. But, strikingly, he doesn't really address the problem he raised in Chapter 1. He still does not present a borderline case of vague consciousness. He does not tell us how to conceive of such cases. Or at least, he does so no more than he could easily have done without the concept of consciousness*. In Chapter 5 he defends honeybee consciousness and box jellyfish non-consciousness. So presumably he could say something like "since jellyfish aren't conscious and bees are conscious, any borderline-conscious animals would have to be somewhere between those two." But that gestural remark depends not at all on the concept of consciousness*, and it's just the sort of handwavy thing that ordinarily fails to satisfy those who object in principle to the existence of borderline cases of consciousness.

I am left, then, thinking that a piece of the puzzle is missing: an explanation of why we should allow the existence of borderline cases of consciousness despite our difficulty of really clearly conceiving of such cases.

Fortunately, that missing piece is just what I supply in my own paper on borderline consciousness.

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[1] Qualification here: Tye treats consciousness* as a physical property and thus zombies as physically possible, though presumably no particles lacking consciousness* have been observed in our universe (though there's a question of how we could know that). Zombies are thus, on his view, not physically identical to us but only identical to us with respect to the functional side of their physical properties, i.e., how every particle interacts with other physical particles. This difference between Tye's and others' treatment of zombies doesn't matter, I think, to the argument of this post.

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Related:

Borderline Consciousness, When It's Neither Determinately True nor Determinately False That Consciousness Is Present (article in draft)

An Argument for the Existence of Borderline Cases of Consciousness (Aug 18, 2021).