The following is a rather simple (simplistic?) argument against certain forms of physicalism*, specifically, those forms which identify the conscious mind with physical processes of the brain. The argument starts with the principle of the indiscernibility of identicals (thank you, Leibniz), which is usually uncontroversial:
If A and B are one and the same thing, then whatever properties belong to A also belong to B.
For example, if Barack Obama and the forty-fourth President of the United States are one and the same person, then if Barack Obama was born in Hawaii, the forty-fourth President of the United States was born in Hawaii.
We can flip this principle around and use it to establish that A and B are not one and the same thing. If A has a property that B does not have, then A and B are not identical. Barack Obama has the property of being born in Hawaii. My father does not have that property (sadly). Therefore, Barack Obama is not my father.
And this sets up the argument against the form of physicalism described above: If your conscious mind is identical to the physical processes of your brain (or some subset of those processes), then whatever properties belong to the one will belong to the other. But this doesn’t appear to be the case.
The physical processes in your brain are in principle accessible to you, or me, or anyone. Brain surgeons could open up your skull and peer inside. They could hold up a mirror for you to see what they see. The proceedings could be televised to the world. With adequate technology, we could in theory peer at every neuron and every neural firing of your brain.
But your conscious experience remains only accessible to you. At no point during such a surgery would we be able to “see” what you were experiencing. In other words, your conscious mind has a property that the physical processes of your brain do not: your conscious experience is accessible only to you.
To put the argument in a slightly more formal way:
- If your conscious mind and the physical processes of your brain are one and the same thing, then whatever properties belong to your conscious mind also belong to the physical processes of your brain (or some subset thereof).
- Your conscious mind has a property that does not belong to the physical processes of your brain: it is accessible only to you.
- Therefore, your conscious mind is not identical to the physical processes of your brain.
Now, one objection would be to say that this argument begs the question: it assumes, in premise 2, that the physical processes of your brain do not have the property of being conscious. This objection, however, ignores the actual property that is being highlighted. Premise 2 doesn’t say that the physical processes are not conscious; rather, it says that they are accessible (i.e., measurable, observable, etc.–a loaded “etc.” I admit) and that your conscious mind is not accessible. Does the objector deny this?
The premise is not unreasonable, at least on the surface. Does anyone actually think that we can access or observe someone else’s conscious experience from a third-person perspective? (Transferring conscious experience–say, by stimulating your own brain with signals from another brain, giving you a parallel first-person experience–doesn’t count.) Yet third-person observability is often built in to the way we define the physical world (rightly or wrongly). We laud scientific investigation, understood as the investigation of the physical world, for the fact that it rests on observation and measurement. Appeals to invisible, unmeasurable (from the third-person perspective) entities are, it would seem, precisely what physicalists want to avoid. Yet, quite obviously, your own conscious experience is real and observable…to you–and, seemingly, only to you.
I see the debate over the argument going two directions: 1) an objector might try to reject the principle of the indiscernibility of identicals (the most common objection I’ve gotten in casual conversation), or 2) one might claim that, even though conscious properties are not accessible like other physical properties, they are still physical. This implies that consciousness is a sui generis, utterly unique physical property–a claim that strikes me as ad hoc.
Please feel free to let me know what you think in the comments below.
*I understand “physicalism” to mean, minimally, that the fundamental elements of the world are non-conscious and non-intentional. Any conscious mind would have to be made by combining non-conscious, non-intentional parts. In other words, I raise no quibble here with my panpsychist friends.