In Amber Ross’s recent dissertation ‘Inconceivable Minds’ she offers arguments against both property dualists and a recent form of physicalism. Ross argues against two popular anti-physicalist arguments: the conceivability argument (a.k.a zombie argument) and the knowledge argument (a.k.a. Mary’s room). Ross also argues against a recent a posteriori physicalist—or what Chalmers calls type B physicalist—argument dubbed the ‘phenomenal concept strategy’. Hereafter, when I say physicalist I mean a posteriori physicalist.
Against the physicalist phenomenal concept strategy
Ross’s goal is to show that there is a problem in the ‘phenomenal concept strategy’. These a posteriori physicalists—as opposed to a priori physicalists–are conceptual dualists in that they accept that something significant happens to Mary when she first sees red. Mary learns a new phenomenal concept ‘red experience’. Mary doesn’t learn a new fact, but she thinks about old facts in a new way. (This seems like a slight of hand to me, but I’ll leave that aside.) These physicalists accept that zombies are conceivable while denying that they are metaphysically possible. The reason that we can conceive of zombies and the reason for the explanatory gap is because of the two different ways in which we think about consciousness, and it’s not because there is something more than physical stuff, so they say.
The strategy for the physicalist is to give a full physical explanation for why we can conceive of zombies.
… even if consciousness cannot be physically explained, we might be able to physically explain the key psychological features and our epistemic situation. If we could physically explain why we are in such an epistemic situation, we would have done the crucial work in physically explaining the existence of an explanatory gap. (Chalmers 2010: 314)
Unlike the property dualists, these physicalists say that the zombies are in the same epistemic situation as us and we will have a physical explanation for the explanatory gap. If we’re in the same epistemic situation it will remove the justification to think that property dualism is true of our world while not being true in the zombie world, hence saving physicalism.
Chalmers says we share an epistemic situation if we:
“have corresponding beliefs, all of which have corresponding truth-value and epistemic status, as equally justified …” (2007: 177)
So, for example, you and twin-you on twin-earth would share the same epistemic situation with regards to beliefs about H2O and XYZ even though the content of your beliefs are different.
Chalmers argues that we don’t share our epistemic situation with zombies:
Why think that zombies do not share our epistemic situation? The first reason for this is intuitive. On the face of it, zombies have a much less accurate self-conception than conscious beings do. I believe that I am conscious, that I have states with remarkable qualitative character available to introspection, that these states resist transparent reductive explanation, and so on. My zombie twin has corresponding beliefs. It is not straightforward to determine just what content these beliefs might possess. But there is a strong intuition that these beliefs are false or at least that they are less justified than my beliefs. (2010: 317)
Chalmers’s response here will probably not worry the physicalist. Ross considers three other anti-physicalist responses (82) that show that we’re not in the same epistemic situation, and concludes that the physicalist should not be worried by those objections. But Ross does offer a novel objection that does not beg any questions and shows that we’re not in the same epistemic situation as zombies. If it turns out that there is a difference in truth values between your utterances and the corresponding zombie utterances, this would show that we are not in the same epistemic situation.
In our world we can consider a person and their phenomenal invert, e.g., a person may see as green what another sees as red yet remain physically, functionally, and intentionally identical. Next think about our corresponding zombie twin that considers a zombie schmenomenal invert. While we have phenomenal properties in our world, our zombie-twins have schmenomenal properties that have the physical, functional, and intentional features of corresponding human phenomenal states while not having the phenomenal content. The zombie would need to consider a zombie that is identical in the physical, functional, and intentional properties while the schmenomenal properties are inverted. But the schmenomenal properties just are the physical, functional, and intentional properties. It would be inconceivable to conceive of something identical and at the same time inverted, hence the title Inconceivable Mind. The upshot is that we don’t share the same epistemic situation as the zombies, and the phenomenal concept strategy is undermined. At this point the option remaining to the physicalist could be to say that while we aren’t in epistemically identical situations, we’re in epistemically similar-enough positions.
Against property dualism’s conceivability to possibility principle
Here’s an older version of the conceivability argument that will suffice for our purposes.
- Zombies are conceivable
- Whatever is conceivable is possible
- Zombies are possible
- Physicalism is false
The conceivability to possibility move is controversial. In order to go from conceivability to possibility (epistemic to modal), Chalmers wants a notion of conceivability that isn’t dependent on a particular subject; he wants a purely rational notion of it. But as Ross notes, conceivability is always relative to an agent; for what would conceivability be without a conceiver.
Consider an IREA–an ideally reasonable epistemic agent–that makes perfect judgments given whatever content and concepts that she has epistemic access to. She is ideally reasonable, but not omniscient. If there’s any way to bridge the gap between conceivability to possibility, it will be by this agent. Next consider an IREZA: an ideally reasonable epistemic zombie-agent. The IREZA will make judgments that are functionally equivalent to the IREA, with the difference being that IREZA uses schmenomenal concepts, while the IREA uses phenomenal concepts. But there’s a problem as was noted in the example of the zombie-invert. The IREZA will think the zombie-invert is conceivable when it in fact is not. Due to the very nature of the IREZA, she will be unable to notice her mistake even though she is ideally reasonable.
This is a problem for the property dualist’s conceivability argument, because if zombies are metaphysically possible then it is possible for an ideally reasonable epistemic agent to be mistaken about their conclusions. If an ideally reasonable epistemic agent can’t secure possibility from conceivability, then no one can. So, ironically, the metaphysical possibility of zombies undermines the conceivability to possibility inference used to infer property dualism.
Against the Knowledge argument
Ross argues that the explanatory irrelevance of consciousness is a bigger problem to the anti-physicalist arguments than property dualists admit. As Chalmers says:
… it seems that consciousness is explanatorily irrelevant to our claims and judgments about consciousness. This result I call the paradox of phenomenal judgment. (1996: 177)
Ross takes this explanatory irrelevance to undermine the knowledge argument. I won’t go into the specifics of this argument here. I can’t say I felt the full force of this argument, but that may be because I didn’t understand it.
Ross, Amber. Inconceivable Minds.
Chalmers, David. The Conscious Mind. 1996.
Chalmers, David. The Character of Consciousness. 2010