A concise way of spelling out the Humean theory of motivation is that an agent will do whatever maximizes expected desire satisfaction. And a concise way of spelling out instrumentalism is that it is rational for an agent to do whatever maximizes expected desire satisfaction. Instrumentalism is sometimes called the Humean theory of practical rationality, so one could call the conjunction of the Humean theory of motivation and instrumentalism the double-Humean view.
In “The Normativity of Instrumental Reason,” Christine Korsgaard argues that the double-Humean view makes practical irrationality impossible:The problem is coming from the fact that Hume identifies a person’s end as what he wants most, and the criterion of what the person wants most appears to be what he actually does. The person’s ends are taken to be revealed in his conduct. If we don’t make a distinction between what a person’s end is and what he actually pursues, it will be impossible to find a case in which he violates the instrumental principle. (230)If maximizing expected desire satisfaction is what it is rational to do (as instrumentalism says) and also what one will do (as the Humean theory of motivation says) it is hard to see how one can act irrationally. According to Korsgaard, Hume not only says that “people don’t in fact ever violate the instrumental principle. He is actually committed to the view that people cannot violate it” (228). If the instrumental principle is the sole principle of practical rationality, this will mean that practical irrationality is impossible. This would be a strange and surprising consequence, and to avoid having to accept it, we might be moved to reject either the Humean theory of motivation or instrumentalism. First, I will explain why exactly it would be a problem for a double-Humean view if it left no room for practical irrationality. I will focus particularly on Douglas Lavin's logical interpretation of the error constraint, and Korsgaard's argument that the double-Humean view will have bad consequences for our ability to regard agents as capable of action. Unlike many recent commentators, I hold that an agent can be subject to a principle even if there is no logically possible action she could do to violate it, and I will present examples of such agents. Nevertheless, Korsgaard and Lavin are right that double-Humeans must account for practical irrationality. This is not because of any formal constraints on normativity, but because practical irrationality exists, and our theories need to reflect this fact. Then I will lay out the two components of the double-Humean view in a more precise fashion and consider the best reasons for accepting them. The Humean theory of motivation should be accepted because it gives the best explanation of how we deliberate and act. While some philosophers have been moved to accept instrumentalism because the considerations it presents as normative have a role in explaining action, this is not a good reason to accept it. We should accept it because it correctly accounts for an important group of our normative judgments. Finally, I will respond to Korsgaard by showing how the double-Humean view can account for just as much practical irrationality as there is. The Humean theory of motivation and instrumentalism should be filled out in ways that measure the agent’s actual desires differently. When determining how agents will be motivated, we should look at the balance of motivational forces that desire produces in them at the moment of action. When determining what it is rational to do, we should look at dispositional desires. As I will argue, this way of setting up the double-Humean view leaves exactly the right amount of space for practical irrationality, while achieving the desiderata that motivate both sides of the position.
Sunday, August 02, 2009
One of the papers I've been presenting this summer on the Moral Naturalism World Tour, "How Double-Humeans Can Make Room for Error", is now available for download. I'm going to send it off to a journal in about a week, so if you want to read it and correspond with me before I do that, now's your chance! Here's the introduction of the paper:
by Neil Sinhababu at 8/02/2009 11:11:00 am