Here’s a fun argument for dualism.
What is a part of the body is a matter of social convention.
Persons are explanatorily prior to social conventions.
So, probably, persons are not bodies.
I think (2) is undeniable. And (1) is a not uncommon view among people thinking about prostheses, implants, transplants and the like.
That said, I think (1) is just false.
Analytic philosophers like to reduce. But not much work has been done on reduction of parthood. Here’s an attempt, no doubt a failure as most reductive accounts are. But it’s worth trying.
Suppose that necessarily everything has causal powers. Then we might be able to say:
Some consequences:
Transitivity
Reflexivity
If nothing other than x shares a token causal power with x, then x is mereologically simple and does not enter into composition. Plausibly nothing shares a token causal power with God, so it follows that God is mereologically simple and does not enter into composition.
How does this work for hard cases where parthood is controversial?
Suppose I lose a leg and get a shiny green prosthesis. If the prosthesis is a part of me, then the prosthesis’ power of reflecting green light is a power I have. It seems about as hard to figure out whether the power of reflecting green light is a power that I have as it is to figure out whether the prosthesis is a part of me. So here it is of little help.
Suppose I am plugged into a room-size heart-lung machine. Is the machine a part of me? Well, the machine has the power of crushing people by its weight. It seems intuitively right to say that by being plugged into that machine, I have not acquired the power of crushing people. So it seems that it’s not a part of me.
Is a fetus a part of the mother? Here, maybe the story is some help. The fetus eventually acquires certain powers of consciousness. These do not seem to be powers of the mother—she can be conscious while the fetus is awake. So, once consciousness is acquired, the fetus is not a part of the mother. But earlier, the fetus as the power to acquire these instances of consciousness, and the mother does not seem to, so earlier, too, the fetus does not seem to be a part of the mother. Here the story is of some help, maybe.
However, one doesn’t need all of (1) for some of the applications. The “only if” part of in (1) is sufficient for the heart-lung machine and pregnancy cases.
Any pretty simple component of us can be replacement by a functionally equivalent prosthesis that isn’t a part of us without affecting our mental functioning.
It is not possible to replace all our pretty simple components by prostheses that aren’t part of us without affecting our mental functioning.
Hence, we are not wholly constituted by a finite number of pretty simple components.
This argument tells against all materialisms that compose us from pretty simple components. How simple is “pretty simple”? Well, simple enough that premise 1 be true. A neuron? Maybe. A molecule? Surely. It doesn’t, however, tell against materialisms that do not compose us from pretty simple components, such as a materialism on which we are modes of global fields.
Let’s idealize the decision process into two stages:
Intellectual: Figure out the degrees to which various options promote things that one values (or desires, judges to be valuable, etc.).
Volitive: On the basis of this data, will one option.
On an idealized version of the soft-determinist picture, the volitive stage can be very simple: one wills the option that one figured out in step 1 to best promote what one values. We may need a tie-breaking procedure, but typically that won’t be invoked.
On a libertarian picture, the volitive stage is where all the deep stuff happens. The intellect has delivered its judgment, but now the will must choose. On the best version of the libertarian picture, typically the intellect’s judgment includes a multiplicity of incommensurable options, rather than a single option that best promotes what one values.
On the (idealized) soft-determinist picture, it seems one could replace the mental structures (“the volitive faculty”) that implement the volitive stage by a prosthetic device (say, a brain implant) that follows the simple procedure without too much loss to the person. The actions of a person with a prosthetic volitive faculty would be determined by her values in much the same way as they are in a person with a normal volitive faculty. What is important is the generation of input to the volitive stage—the volitive stage is completely straightforward (except when there are ties).
On the libertarian picture, replacing the volitive faculty by a prosthesis, however, would utterly destroy one as a responsible agent. For it is here, in the volition, that all the action happened.
What about replacing the intellectual faculty by a prosthesis? Well, since the point of the intellectual stage is to figure out something, it seems that the point of the intellectual stage would be respected if one replaced it by an automated process that is at least as accurate as the actual process. Something else would be lost, but the main point would remain. (Compare: Something would be lost if one replaced a limb by a prosthetic that functioned as well as the limb, but the main point would remain.)
So, now, we can imagine replacing both faculties by prostheses. There is definite loss to the agent, but on the soft-determinist picture, there isn’t a loss of what is central to the agent. On the libertarian picture, there is a loss of what is central to the agent as soon as the volitive faculty is replaced by a prosthesis.
The upshot of this is this: On the soft-determinist picture, making decisions isn’t what is central to one as an agent. Rather, it is the formation of values and desires that is central, a formation that (in idealized cases) precedes the decision process. On the libertarian picture, making decisions—and especially the volitive stage of this process—is central to one as an agent.
