Wednesday, September 22, 2010

Instrumental desire

Let NORID be the thesis that there is no instrumental desire (NID) or instrumental desire reduces (RID) to non-instrumental desire plus belief about what is a means to what (e.g., an instrumental desire for jogging reduces to a non-instrumental belief that jogging promotes health and a non-instrumental desire for health).

One argument for NORID is something I got from Mark Murphy. Desires explain actions. But if M is a means to an end E, we do not need to posit any desire for M to explain the pursuit of M—all we need to posit is a belief that M promotes E and a desire for E.

Here are two more arguments, perhaps unoriginal.

Argument 1: Inertia. Start with this premise:

  1. If x has an instrumental desire for M, then x believes that M is a means to something that x desires.
Suppose I have a non-instrumental desire D for M, which I believe is a means to E and to nothing else I desire, and suppose the desire does not reduce to non-instrumental desire and belief. Now, suppose I lose the belief that M is a means to E. There may be connections between desires and beliefs, but unless the kind of reduction that RID envisages holds, a mere change of belief does not immediately result in the loss of a desire. There is an inertia in the mental life. Therefore, after I have lost the belief that M is a means to E, my irreducible desire for M continues. Moreover, the same inertia makes it plausible that the desire does not immediately change in nature, from instrumental to non-instrumental. (This assumes that the difference is intrinsic. That might be a point worth questioning.) But if so, then for a while I have an instrumental desire for M and no belief that M is a means to anything that I desire. Which contradicts (1).

Argument 2: Rationality. Suppose I am perfectly rational and I non-instrumentally desire E with strength dE. Suppose I know with certainty that M is a necessary and sufficient means to E. Then, rational as I am, I will be motivated to pursue M at least with strength dE. Now suppose that I instrumentally desire M with strength dM. Surely a desire that does not reduce to non-instrumental desire and belief adds to motivation. So, now, I will be motivated to pursue M with strength greater than dE (maybe dE+dM?). But it is irrational to be motivated to pursue a means with a strength beyond one's perfectly rational desire for the end, and that was dE. So, NORID is true of a perfectly rational being. But it is plausible that NORID is also true of imperfectly rational beings. First, it would be odd if a basic kind of desire—instrumental desire—were never rational. Second, we can say the following. The above argument shows that if I have an irreducible instrumental desire for M, that desire adds to the motivational force of my desire for E combined with my certainty of the necessity and sufficiency of M. But whatever it adds to that motivational force goes over and beyond the merely instrumental motivation for M, since the merely instrumental motivation for M is fully accounted for by the motivation in favor of E combined with my certainty of the necessity and sufficiency of M.

I am grateful to Dan Johnson for showing me that my arguments do not show that there are no non-instrumental desires, but only that either there are none, or they are reducible.


Heath White said...

Count me an opponent of NORID.

Against the Murphy argument: I believe that pleasure is a good and that ice cream could provide me with some pleasure. However, I am not now eating ice cream. This needs explanation, which your irreducible desires don’t give me.

Against the Inertia argument: this is tricky, but I think I would say that there is a distinction between a belief that M is a means to something I desire (de dicto) and a belief that M is a means to E, which I desire (de re). You could drop a desire for E, thus losing the latter belief, while maintaining the former. The former would be sufficient to maintain the desire for M as an instrumental desire. (I can also see a strategy questioning the intrinsicness of the non/instrumental distinction.)

Against the Rationality argument: I deny “Surely a desire that does not reduce to non-instrumental desire and belief adds to motivation.” In fact, desires for ends, plus beliefs about means, need result in no motivation at all, as per my Murphy comment above. Plus, I am very suspicious of the whole concept of “motivational strength.” Desires are not well conceived of as mental hydraulic forces.

Alexander R Pruss said...

I don't see how the ice cream case is a counterexample to the argument. To make it a counterexample, I think you'd have to (a) posit that you have a desire for pleasure (not just a belief that pleasure is good) and (b) posit that not only are you not eating ice cream now, but you are not motivated to eat ice cream. I think that would make the case puzzling. Granted, that you're not eating ice cream needs an explanation, but presumably the explanation is not hard to come by: you presumably have some reason for doing something other than eating ice cream. What am I missing?

The move against the inertia argument is nice. Still, what if I just say: "drop the belief that M is a means to anything worth having." If desire doesn't reduce to belief, there should still be some inertia--some motivation to pursue M--even after the dropping.

Heath White said...

You are right that my first attempted counterexample conflates doing something with being motivated to do it. For that reason, it fails. But I think there is a real problem with the idea of “motivation” and its cousin, “motivational strength.” For starters: what exactly are the truth conditions of “I am motivated to do X but am not doing X” and “I am more motivated to do X than Y, although I am not doing either”?

I have instrumental beliefs about how to get lots of things I want, without being seriously motivated to take those means. I want money and I can get it by stealing from my employer. I want sex and can get it by raping a woman. I want people to admire me and I can get it by leasing a Jaguar, with every last penny of disposable income. I am not seriously motivated to do any of those things. You can reply that “surely, in some weak sense, you ARE motivated” but then again I would like to know what the truth conditions of that claim are. How do we tell if I am motivated or not?

Consider the analogous view about belief: I believe that P, and I believe that Q if P, and my belief that Q is on the basis of the aforementioned beliefs, so my belief that Q must reduce to those two beliefs. I think you could run analogues of all three arguments for this case. But I don’t know of anyone who has ever defended this view (nor should they, in my opinion).

Alexander R Pruss said...

"I have instrumental beliefs about how to get lots of things I want, without being seriously motivated to take those means."

But in the cases you give, the lack of on-balance motivation surely comes from the reasons you have to the contrary. You'd buy the Jaguar if you could more easily afford it (and there were no needy people to whom you should instead give the money).

I agree about the obscurity of motivation. I think desire has the same obscurity. In the final analysis, I don't actually want desire to play any role in my action theory. So the arguments here are just aimed at people who take the standard view of desire and motivation.