Monday, January 23, 2017

Prosthetic decision-making

Let’s idealize the decision process into two stages:

  1. Intellectual: Figure out the degrees to which various options promote things that one values (or desires, judges to be valuable, etc.).

  2. 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.


Heath White said...

I don't follow here. On either picture, the volitive stage is effectively an i/o device: it takes whatever the intellectual stage delivers, and outputs a volition (or whatever). Either view could have simple commensurable inputs, or complex incommensurable inputs.

It appears that in/commensurability is doing the work of deep/shallow for you, but I don't know what that has to do with in/determinism or libertarianism.

Alexander R Pruss said...


I took for granted the observation that the compatibilist can't handle incommensurable inputs (except by positing some pseudo-random decision procedure?). I got the observation from my student Rob Elisher. Of course, we could be wrong on this--I take it you think we're wrong?

Heath White said...

Yes, I think this is wrong.

Some people (maybe you’re one) have the view that (a) options are typically incommensurable in their values, also (b) there is often a rational choice to be made among them. This makes no sense to me. Either there is or is not a partial ordering ‘>’ among options. If there is, the output of the intellectual module can be something like “Option X dominates all the other options” and that is all the commensurability you need for rational decision-making. There is no reason a deterministic volitive mechanism could not act on this kind of input. If there is no such ordering, and the intellectual system cannot say anything like “Option X dominates all the other options”, then there is no rational choice to be made. Having libertarian free will won’t help.

The other way around: Suppose we say the intellect just outputs various options with incommensurable values attached to them. A deterministic mechanism, we’ll suppose, cannot choose between them on the basis of a rational comparison of their values. But it doesn’t follow that it cannot choose at all. (Compare: the DNA from Mom and Dad are combining to create the DNA for Kid. At the level of description used in biology, which genes Kid gets is “random.” At the level of physics, it may not be random at all.) And I don’t see how a libertarian volitive module can choose on the basis of their values either. If they’re genuinely incommensurable options, it’s just hand-waving to say that somehow the libertarian will chooses rationally.