Physicalist Q&A

 Q: Why can we conceive of the mind being separate from the body? 

A: Co-referring concepts are not always applied on the basis of the same evidence. For instance, even though water is composed of H20, the evidence that leads us to apply our ‘water’ concept (the presence of watery stuff) is not the evidence that leads us to apply our ‘H20’ concept. That is why further scientific investigation is required in order for us to conclude that what fills our lakes and rivers is, in fact, H20. 

When co-referring concepts are not applied on the basis of the same evidence, it can seem conceivable for the referent of one concept to be present in the absence of the other. This is why some people have thought that they could conceive of a world where water was not actually composed of H20. However, in most cases, this apparent possibility can be understood as a world where the evidence that leads us to apply one concept is present in the absence of the other concept’s referent. Thus, when it seems conceivable that water could be present without H20, what we are actually conceiving of is a world where watery stuff is present in the absence of H20. 

Once we understand that watery stuff is only contingently associated with water, we can recognize that the world we are conceiving of is not a world where water is present in the absence of H20 after all. Instead, it is a world where the watery stuff that fills lakes and rivers is a different kind of liquid altogether. 

However, in the case of the mind and body, it does not seem possible to explain their apparent distinctness in this way. This is because, unlike the evidence that leads us to apply our ‘water’ concept, our evidence for consciousness (our direct acquaintance with phenomenal properties) is not contingently associated with the actual presence of consciousness. Rather, when our evidence for phenomenal consciousness is present, this evidence entails that consciousness is present as well. Consequently, if it is possible for our evidence for consciousness to be present in the absence of the body, it is possible for consciousness to be present in the absence of the body too. In this sense, the appearance of mind-body distinctness is robust in a way that the appearance of water-H20 distinctness is not. 

The apparent conceivability of the mind being separate from the body raises two questions that physicalists must answer: First, why do the mind and body appear to be distinct? Second, why is this appearance of distinctness robust? The answer to the first question is that the mind and body appear distinct because we do not apply our mental and physical concepts on the basis of the same evidence. The answer to the second is that this appearance is robust because the evidence that leads us to apply our mental concepts is necessarily associated with the actual presence of consciousness. 

These answers provide the physicalist with grounds for denying the link between the robust conceivability of mind-body distinctness and metaphysical possibility: Co-referring concepts are not always applied on the basis of the same evidence and it is possible for one co-referring concept, but not the other, to be applied on the basis of evidence that is necessarily associated with its referent. Since these conditions can give rise to a robust, but misleading appearance of distinctness, there is no link between robust appearances of distinctness and metaphysical possibility. Although conceivability can provide defeasible support for an inference to possibility, this support can be overcome by a posteriori evidence for metaphysical necessities. The physicalist can appeal to our scientific discoveries about the brain as sufficient evidence of this sort. 

Q: If it is possible to robustly conceive of metaphysical impossibilities, how can conceivability be evidence for possibility?

A: The evidential status of conceivability can be understood in simple, bayesian terms. Robust conceivability requires two distinct concepts that are not applied on the basis of the same qualitative evidence. If I am thinking of two distinct things, I must have two distinct concepts that, in almost all cases, will not be applied on the basis of the same evidence. By contrast, thinking of one thing is possible without having two distinct concepts. Consequently, the fact that I can robustly conceive of one thing in the absence of the other is more readily predicted by the hypothesis that I really am conceiving of two distinct things. So even though we can robustly conceive of metaphysical impossibilities, that does not stop conceivability from providing defeasible evidence of possibility. 

Q: If consciousness is physical, why does there seem to be an explanatory gap regarding the emergence of consciousness in nature? 

A: Normally, we can explain some natural phenomenon by discovering what sort of thing it is and describing how that sort of thing is realized by more basic physical facts. This is possible because the sorts of things that science usually explains can be essentially characterized in causal-structural terms. For instance, we can give a scientific account of water by first discovering that it is a kind of liquid that has certain characteristic causes and effects. We can then describe the lower level physical phenomena that come together to realize those characteristics. This allows us to understand what empirical facts are responsible for the presence of water and why they are sufficient. 

But in the case of consciousness, we cannot arrive at any substantial characterization of what sort of thing it is by appealing to causal-structural characteristics. Such a characterization is not a conceptual truth associated with our concept of consciousness. Furthermore, we cannot directly arrive at one through empirical investigation because we apply our mental concepts on the basis of our direct acquaintance with phenomenal consciousness itself. Since our direct acquaintance with experiences does not lead us to any conclusions about it’s potential causal-structural characteristics, we can only arrive them via an a posteriori identification of consciousness with some physical phenomenon. 

However, if such an identification is made, then once we have provided an explanation of the identified physical phenomenon, no further explanation of consciousness is required. This simply follows from the fact that, when two things are identical, an explanation of one is an explanation of the other. What makes the case of consciousness unique is that an a posteriori identification is required in order for an explanation to proceed. 

Q: Suppose Mary lives in a black and white room where she learns every physical fact relevant to the experience of color. Upon leaving the room and seeing the color red for the first time, it seems like she will come to learn something new. But if facts about consciousness are physical facts, how could this be possible? 

A: When Mary leaves her room and sees the color red , she is directly acquainted with the color red for the first time. On this basis, she learns that “*this* is what it is like to see red”. This is a new belief about a fact that she already knew in her room via a different thought. Her new belief involves the use of a new demonstrative concept that is applied on the basis of her direct acquaintance with the property that it refers to. She could not have formed this belief in her room because it involves a demonstrative that is specifically used to refer to the color red on the basis of her direct acquaintance. If she had used a demonstrative concept to refer to the color red while she was inside of her room, the concept would have had a distinct kind of originating use. Since concepts are individuated by their originating uses, her new knowledge could only be acquired by actually having an experience of red.