DOI 10. 1007/s 1 1098-004-4917-7 J. DREIER · DOI 10. 1007/s 1 1098-004-4917-7 J. DREIER ... So my critical discussion is offered in the spirit loyal ... Theory benefits by taking

Philosophical Studies (2005) 124: 199-219 ? Springer 2005 DOI 10. 1007/s 1 1098-004-4917-7

J. DREIER

PETTIT ON PREFERENCE FOR PROSPECTS AND PROPERTIES - DISCUSSION

Philip Pettit's work on Decision Theory continues to be among the most valuable philosophical contributions in the area. I have always been envious of his ability to combine mastery of the technical details with real philosophical insight. The papers in the second section of Rules, Reasons, and Norms are no exception. So my critical discussion is offered in the spirit loyal opposition.

Section 1 explains how I -understand the subject matter, Decision Theory, and the second describes Pettit's suggestion in "Decision theory and folk psychology" for an amendment to the theory. Section 3 raises a question about a distinction crucial for Pettit's main thesis, namely, the distinction between desiring prospects and desiring properties. Section 4, the longest and most substantial section, develops and replies to his arguments for the amendment. Briefly: Pettit thinks that Decision Theory benefits by taking on board an extra assumption, the "assumption of desiderative structure"; I say there is no reason to accept the new assumption.

1. WHAT IS DECISION THEORY?

Decision Theory, also known as Expected Utility Theory, en- joys an uneasy and ambiguous status among philosophers and economists. On the one hand, it is sometimes seen as a very "thin" theory of rational choice, preference, and action, imposing a kind of measure or structure on the elements of our choices no matter what they might be - or at least so long as they conform to some rather weak constraints. On the other hand, it is sometimes seen instead as a substantive, controver- sial and contentful account of rationality, a normative theory,

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or else an empirical theory of the way typical agents really do make their choices. Which is it, really?

In the first instance, Decision Theory has a formal skeleton: a collection of axioms from which a central theorem can be proved. These axioms are also the 'constraints' I just men- tioned. The skeleton has no normative or empirical content whatever. But, like any formal theory, it can be given a content by one or another interpretation of its uninterpreted vocabulary, along with an interpretation of the force of its axioms. The vocabulary item ripe for interpretation is the one that gets called the "preference relation" in the formal explication, and the force of the axioms could be empirical, as when we think of them as providing constraints that any agent (or almost any agent) will satisfy, or it could be normative, as when we think of them as constraints that anyone will satisfy on pain of irratio- nality. If we choose an interpretation, we can then ask whether the interpreted theory is true, and we can check by investigating the axioms under the proposed interpretation. And if we decide that it is true, then we get the central theorem for free.

The central theorem of Decision Theory is the Expected Utility Theorem. It is worth taking a moment or two to explain what it says, even though the main idea will be familiar. It says that preferences that satisfy the axioms (and only preferences that satisfy them) will be representable by an expectational utility function. A utility function assigns real numbers to prospects - generally thought of as states of affairs or propositions - and it represents a collection of preferences just in case for any pair of prospects, A and B, it assigns a higher number to A than to B if A is preferred to B, a higher number to B if B is preferred, and the same number if the agent is indifferent between the two. A utility function is expectational just in case it assigns to each prospect a utility that is equal to the expectation of the utility of the prospect. The expectation of the utility of a prospect, say the prospect that I go to the beach tomorrow, is simply the weighted average of the utilities of subprospects, say the two sub-prospects that I go to the beach tomorrow and it rains, and that I go to the beach tomorrow



PETTIT ON PREFERENCE FOR PROSPECTS AND PROPERTIES 201

and it does not rain, where the weightings are the probabilities of the sub-prospects (conditional on the prospect; but like Pettit I will generally use examples that will render this conditional- ization irrelevant).

In case all of that sounds daunting and unfamiliar let me restate it in a less precise but perhaps more familiar way. What is the utility for me of going to the beach tomorrow? Well, we can apply the formula that most of us have learned to associate with Decision Theory. If it rains tomorrow, the utility for me of going to the beach is low, say 3. If it does not rain, the utility for me is high, say 15. My view about the weather is that there is a 2/3 chance of rain. So the expected utility of going to the beach for me is 2/3 times 3, plus 1/3 times 15, which is 7. Suppose now that I could instead choose to go to a basketball game, whose utility for me will be 10, independent of the weather. Then I prefer going to the basketball game, since its utility is higher.

Is this a good way for me to work out whether I ought to go to the basketball game? No. Imagine that I asked you to try it. What is your utility for going to the beach in the rain? If it doesn't rain? What about for the basketball game? You may well say that you have no idea. You don't have any way to figure out what your utility is for various things. But here's where Decision Theory steps in. It finds a utility function for you, and it makes sure that the function it has chosen is one that represents your preferences (so that you will find that it has assigned a higher utility to the prospect that you do, in fact, prefer) and that it is expectational (so that the utility it assigns to your going to the beach in fact matches the sum of products of utilities with probabilities of the sub-prospects, going to the beach in the rain and going to the beach when it doesn't rain). So, although you may have no idea how to go about maximizing your expected utility, you needn't worry. Decision Theory takes care of the choice of function and the assigning of utilities. You go ahead and do just what you prefer, and lo and behold, you will indeed be maximizing the expectation of your utility. What a relief!



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2. PETTIT'S ASSUMPTION OF DESIDERATIVE STRUCTURE

To return to my first question: which kind of theory is Decision Theory, really? The answer is that as a formal theory it admits of both a normative and an empirical interpretation. It is another question whether it comes out true under one or both or neither. A more tractable question is how thick or thin the theory is. Does it impose strong, substantive constraints (or make powerful empirical predictions), or is it more a matter of setting out what sorts of constraints we should expect anyone we can understand as a choosing agent to satisfy? My own view is that it is much closer to the latter. The constraints of Decision Theory are relatively easy to satisfy, and for the most part we all do satisfy them, at least to a close approximation. Philip Pettit's work on Decision Theory is in the same spirit. In "Reasons and Choice", Part II of Rules, Reasons, and Norms, his papers build up from pure 'folk psychology', in which rational explanation is understood as a species of 'programming explanation', to Decision Theory understood as a part of folk psychology, and then through some meatier explanatory posits useful in economics and social science. I will focus on the second step, in which Pettit suggests that Decision Theory, though unobjectionable in its own way, needs to be supplemented by what he calls the assumption of Desiderative Structure.

In standard Decision Theory, the objects of preference' are prospects, typically states of affairs. Sometimes (as in Jeffrey's theory) they are propositions. It is somewhat unnatural to speak of preferring a proposition, but I will suppose that it is harmless. The structure of a field of propositions is, as far as I can tell, isomorphic to the structure of states of affairs. In any case, prospects are indexed by sentences (or sometimes by infinitives, as when I prefer to ride my bike, but even here we can take it that what I prefer is that I ride my bike). Pettit thinks that we do desire and prefer prospects. But he adds that when we do, we desire and prefer them for the properties that are realized in them, and the most fundamental preferences and desires we have are for these properties. This is the assumption of desiderative structure.




Again: Pettit does not deny that we prefer prospects. The main claim is not that Decision Theory is incorrect in saying that we do. It is rather that Decision Theory is incomplete in leaving out the more fundamental sort of preference: preference for properties.

Pettit has a number of arguments for the assumption of desiderative structure, and a number of complaints against a Decision Theorist who would leave it out of the picture. I will explain why I think these arguments do not succeed. In each case, I think Pettit has identified a misleading way of thinking about preferences or utility, but in each case I disagree about the diagnosis.

The assumption of desiderative structure says "that there are two quite different sorts of objects that desires may have - prospects and properties - and that the desires that we form for different prospects are determined by the properties that we think they have. Any prospects that we desire, any prospects that we prefer to the relevant alternatives, we desire for the properties they display or promise to display."2 I think we need a little help understanding what it is to desire a property, even though there are perfectly ordinary English locutions in which we seem to speak of desiring properties. When Americans en- gage in the "pursuit of happiness", for example, they desire what they pursue, and that's happiness. And happiness is a property. When marking a student's paper, I generally prefer brevity. But what does Pettit mean by saying that we desire prospects for the properties they display? Prospects can display properties either by bearing the properties or (let's say) by containing them. The prospect of my beating Judit Polgar in a game of chess bears this property: unlikelihood. It contains this property: brilliance. In the unlikely prospect of my beating Judit, I personally instantiate brilliance. When something in a prospect instantiates a property, the prospect contains the property. Or, if it is unclear how something can be in a prospect, we could say that when a prospect includes or involves the property's being instantiated, then it contains the property.

As an example, Pettit notes that "the property of travelling will belong to the prospect of my going to London this



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afternoon, and so on." [198] This example (and another he gives later, to be discussed below) involves an irrelevant dis- traction, which I shall mention only to leave it aside. It is that what Pettit presumably wants when he desires "travelling" is not a desire that would be satisfied by a state of affairs in which Frank Jackson travels to Monkey Mia, but only by a state of affairs in which Pettit himself travels. We often say that we want to travel, or desire to drink, or prefer to sit in a comfortable chair, where the syntactic object of the verb is an infinitive, and in such cases what we want is not that the property be instantiated, but rather to instantiate the property. But let's not allow this feature of the example to confuse us. More impersonal desires illustrate the main point more clearly. Suppose that Peter desires that factory farming be abolished. It is plausible that he desires this prospect for a property it contains: freedom from suffering. He prefers the prospect to its alternative because the property he desires is instantiated much more frequently in the prospect he prefers than in its alternative. No doubt he also prefers to instantiate the property himself, but that is no part of the explanation of the preference in question.

3. IS THERE REALLY A DIFFERENCE BETWEEN PROPERTY PREFERENCE AND PROSPECT PREFERENCE?

The assumption of desiderative structure seems plausible on its face. Pettit argues that decision theory is improved by its addition. I will canvass his arguments below. First, though, I want to inspect a potential problem that Pettit himself identifies only to brush it aside. Here is what he says:

But, though properties can be seen ... as distinct sorts of entities from the prospects that involve them, there is a qualification to be made about that representation. This is that, for all we need to say, a property can equally be represented as itself a type of prospect. Ignoring some complications, we can represent the property of being an F as equivalent in all significant respects, for example, to the prospect that there is something that is F: that is, equivalent to the set of possible worlds at which there are Fs. If this representation is preferred, then it will affect the formulation of the assumption of desiderative structure, but it will not alter the substance. The assumption




will not be that we desire properties as well as prospects and desire prospects for the properties that we think they have. Rather, it will be that among the set of prospects there is a special class - those corresponding, for appro- priate properties, to sentences such as 'there is something that is F - and that, for any prospect we desire, we desire it because we see it as involving the realization of one such privileged sort of prospect. [198]

Suppose, for example, that I am considering two prospects: that the corporate income tax rate be 15% and that it be 10%. I prefer the former, and I prefer it because I think that the dis- tribution of money in our population will in that case be more egalitarian. I desire equality, and the 15% tax rate promises more equality. But why couldn't the very same desire be put this way: I desire that there be more equality? Surely there is no difference between the desire for equality and the desire that there be more equality. Or take one of the more personal desires: the desire for some excitement. Why isn't this equivalently describable as the desire that I experience some excitement? Surely they are two descriptions of the same desire. But then, what is the point of the assumption of desiderative structure?

Pettit says that if we adopt the notation of describing all desires, even the ones that he thinks of as property desires, as prospect desires, then we will simply have to restate the assumption of desiderative structure as the assumption that our basic desires have a special sort of prospect as their object. The basic desires' objects will be prospects of the form, there is something that is F, where 'F' names the object of the property desire. But when the assumption of desiderative structure is cast in the new terminology, it begins to look vastly less plausible.

First, if we have an expansive conception of properties in mind, as Pettit does [198], nearly every proposition can be wrenched into the form that there is something that is F. For arbitrary proposition, p, let F be the property of being such that p (for instance, for the proposition that snow is white take the property of being such that snow is white). Then p can be equivalently expressed by saying that there is something that is F; in general, that p is equivalent to that there is something that is such that p. The new sentence is a different (and rather less natural) sentence, but it expresses the same proposition.3 If



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every prospect is a member of the "special class" singled out by the assumption of desiderative structure, then plainly the assumption is vacuous.

So, second, suppose that the class is contracted, by insisting that it includes only prospects that fit the model there is something that is F more intuitively. There are several ways to do this. We could say that the special class includes only universal propositions, for instance, and no singular propositions, or we could say that only existential generalizations and not universal ones count. This would mean that although Philip might like the prospect that Australians are highly educated because he desires (fundamentally) that someone be educated, he could not like it either because he desires that everyone be educated or that Rory be educated. If Philip did desire that everyone be educated, this would have to be because he desired some existentially quantified proposition. This restriction, though, seems completely implausible and utterly unmotivated. Similarly, it seems at least as plausible, and indeed considerably more natural and familiar, to suppose that Philip likes this or that prospect because he desires that Rory be educated, as to suppose that he likes it because he desires that someone or other be educated.

Third, there might be some thought that we never desire conjunctions or disjunctions (or other truth functions) fundamentally, but always because we desire their conjuncts or disjuncts (which could then turn out to be universal propositions). Some examples seem quite plausible. I would like to be rich and powerful because I would like to be rich and I would like to be powerful. I prefer that either there be a Middle East peace or that there be a beautiful performance of Mendelsohn, but only because I prefer each disjunct. However, as a general restriction this one is not plausible at all. If I like diversity, I might want there to be someone who is over six feet tall and someone who is under five feet tall, but not because I want there to be someone who is over six feet tall or someone who is under five feet tall.4

In short, it is hard to see how restricting the special class of prospects to the form Pettit wants could be both contentful and




plausible. To be plausible, the conceptions of property and prospect must be broad, in which case the restriction seems to be vacuous; but to impose any significant restriction the conceptions must narrow, in which case the restriction seems to be arbitrary and implausible.

4. THE THREE ARGUMENTS FOR DESIDERATIVE STRUCTURE

Maybe we can see what sort of restriction Pettit has in mind by looking at the reasons he gives for the inclusion of the assumption of desiderative structure into the folk psychology that decision theory tries to capture. (Again, Pettit thinks that so far as it goes decision theory does capture folk psychology; his worries amount to the concern that it leaves something out.) He says that without the assumption of desiderative structure, decision theory is (i) incomplete, (ii) non-autonomous, and (iii) impractical.

(i) Incomplete. I have to admit that I am not quite sure what sort of incompleteness Pettit is pointing to. In a way, all of the shortcomings of decision theory that might be made good by the addition of an assumption of desiderative structure are shortcomings of incompleteness, since they must be due to its failure to include a true and significant assumption. Further- more, there is a standard assumption of decision theory that is (often) called'completeness', namely, the assumption that every pair of prospects is ordered (in the sense of a weak ordering, so as to include the possibility of ties) by a fully rational agent. Neither of these sense of 'completeness' is what Pettit has in mind. I think his point is that decision theory either gives no explanation of how a person's preferences are determined, or else it gives an incorrect account. Determination here is a somewhat elusive notion. It is not causal. No doubt some of our preferences are caused by our endocrine systems, or by training in our early childhood, and so on, but this sort of causation is not to the point. The kind of determination in question is difficult to elucidate, but generally fairly familiar, I



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believe. An example is in familiar instrumental preferences and desires, as when I want to move to a certain city only because I want to live near my family; here the determined desire is 'for the sake of the determining one.5 Perhaps there are other sorts of rational determination than instrumental, or perhaps there aren't; we needn't take sides.

Does decision theory have anything to say about how preferences are determined, in this sense? I think not. It has something to say about how preferences are related in a coherent person, but nothing to say about how or even whether you might want one thing for the sake of another. As I understand Pettit's point, he does not claim that decision theory is committed to preferences being determined in one way or another. He makes two points. First, he notes that decision theory is committed to a certain principle of co-determination; and second, that a pair of 'natural assumptions' can be added to decision theory to imply a quite specific conception of how preferences are determined. Let's take these in turn.

Principle of co-deternmination of preferences For every prospect, the place of that prospect in a rational agent's preference ordering is determined - given his probability function - simulta- neously with the places occupied by its subprospects; the place of each subprospect is co-determined in the same way with the places occupied by each of its subprospects; and so on down to the ultimate atomic subprospects, if there are any. [206]

Here 'subprospect' is a term of art. In general, prospects may be partitioned into exhaustive and exclusive subprospects as sets may be partitioned into subsets. Subprospects can be thought of conveniently as exclusive disjuncts whose disjunction is the prospect itself. So, for instance, the prospect of fine weather tomorrow might have as subprospects clear blue sky and some clouds, and we might think of the prospect that tomorrow's weather will be fine as the prospect that either there will be clear blue sky or there will be some clouds (and not both!). Adopting some standard technical apparatus, we can think of a prospect as a set of possible worlds, and a division into subprospects as a partition of the set. The question of whether there are any "ultimate atomic subprospects" is, properly speaking, the




question of whether there are propositions implied by no propositions other than themselves and the impossible proposition. Once we are thinking in terms of sets of worlds, an answer is forthcoming: the unit sets of possible worlds (or for convenience, just the individual worlds themselves) are atoms.6

Now in decision theory, the utility of prospects is locked mathematically to the utility of subprospects, as I explained in section 1. But this locking is symmetric, so there is no question of the utility subprospects determining the prospects in the asymmetric sense of my preference for moving to a new city being determined by my preference for living near my family. After all, the utility of the prospects (along with my credences, or probabilities over possible outcomes) equally well deter- mines, in the mathematical sense, the utility of the subprospects. This is why, I presume, Pettit says that they are co-determined. Next,

The principle of the co-determination of preferences easily goes over into the principle of completeness. Two attractive assumptions are sufficient to generate the shift: first, that there are indeed ultimate atomic subprospects; second, that the rational agent's preferences for non-ultimate prospects are determined by his preferences for subprospects, so that his preferences for the ultimate subprospects come out then as basic. [206]

Attractive as these assumptions may be, I must insist, they are no part of decision theory. This point is important, because Pettit argues that the "completeness principle" implied by them (together with proper decision theory) is implausible. I think he's right that the new principle is implausible, but wrong that the implausibility is traceable back to decision theory's letter or spirit.

Let's leave aside the technical question of atoms.7 Here is the 'completeness principle' that Pettit says is implied:

The completeness principle holds that the rational agent assigns a place in his preference-ordering to every possible world and that the place of every other prospect - in effect, every set of possible worlds - is determined by those rankings combined with the agent's probability function. [207]

This time, the determination in question is not symmetric. Rather, it means that whenever you prefer, say, that the



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weather be fine, this must be because of the place in your preference ordering of some clouds and clear blue sky. In turn, some clouds must have its place because of the place of some clouds and there is life on Mars along with the place of some clouds and there is no life on Mars. And the first of those must have its place in your preference ordering because of the places of some clouds and there is life on Mars and there are an odd number of humans in Mexico and some clouds and there is life on Mars and there are an even number of humans in Mexico. Surely Pettit is right that this claim of determination is most implausible.

But, as I insisted, the implausible feature does not come from decision theory. It is an add-on. If it is attractive, as Pettit says it is, then I suppose it is specious. I can dimly see how it might be thought to arise from the spirit of decision theory. Let me see if I can dispel that thought. My point will be that the 'completeness principle' is in fact quite inconsistent with the spirit of decision theory.

First of all, if we are to speak of the 'determination' of logic or coherence, the principle simply isn't true. To see this, consider a simplified logical space in which the atomic prospects are A (I get some action), B (I am bored), and C (I am comatose), and suppose I rank A above B and B above C. Suppose further than my credences are not very optimistic: I assign a probability of 1/3 to each atomic prospect. My ordering and my probability function do not determine the places in the ordering of the disjunctions AvB, BVC, and CVA. Specifically, from the information given so far, you cannot tell whether I prefer action or coma to boredom, that is, whether I prefer AvC to B. So says decision theory, and this certainly seems intuitively right.

Second, think of what further information you might need to have some idea of my preferences concerning the disjunctions. Intuitively, you would need to know to what degree I prefer A to B, and to what degree I prefer B to C. That means you would need to know my utilities for A, B, and C. But, it is quite contrary to the spirit of decision theory to suppose that you might get this information in any way other than discovering




my preferences over the disjunctions themselves! As Pettit himself points out (in the appendix to the paper), utilities are assigned to prospects on the basis of the agent's preferences over 'lotteries' involving them. And these 'lotteries' are nothing but exclusive disjunctions along with probability assignments. In other words, a decision theorist computes the utilities of A, B, and C by inquiring into the agent's preferences among AVB, BVC, and CVA, and also her probabilities over A, B, and C. The utility assignment that results is, as I noted in section 1, a theoretic construct that in effect summarized a lot of information about a coherent agent's preferences and credences. So, far from being asymmetrically determined by my utility for A, B, and C, my preferences over their disjunctions determine those utilities. At least, so it is according to the founding spirit of decision theory.

To summarize, it is not very plausible that the only things we desire for themselves are maximally specific ways that the world could be, with everything else desired because it makes it more or less likely that the world should turn out exactly this or that way. Thinking in decision theoretic terms may tempt some theorists to suppose that the implausible thing is so, but decision theory itself is in no way implicated, and in fact has a spirit quite contrary to the implausible thesis.

(ii) Non-practical. Pettit thinks that (a) decision theory doesn't give us any helpful practical advice, and (b) the assumption of desiderative structure can help. My response will be that he is fundamentally right on the first count, but wrong on the second.

Pettit writes,

If someone uses decision theory as a calculus, then he forms his preferences over options on the basis of considerations such as 'My subjective probability for "p" is 3/4' and 'My subjective utility for "q" is 7'. This means... that he forms his preference on the basis of self-ascriptions of beliefs and desires. The considerations deployed can equally well be cast as follows: 'I believe to degree 3/4 that p' and 'I desire that q with an intensity of degree 7'. [214]



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Let's call this method of deliberating over choices, "aiming at utility". As Pettit rightly explains, people do not really (typically, at least) aim at utility, nor should they. Preferences and desires do figure in my practical deliberation, but they do not figure as goals. Instead, they figure in the 'background' (Pettit and Smith, 1990). Suppose I desperately want the respect of my colleagues. Then often I will aim in my deliberations at the prospect, that I gain the respect of my colleagues. I will work hard to write respectable papers, I'll plan carefully my contributions to committee meetings, and so on, all with the goal in view of gaining respect. The explanation for why I reason in this way will properly make reference to my desire, or preference, that I gain the respect of my colleagues. But that doesn't mean that my aim is to satisfy my own desires. My goal is not desire satisfaction; it is given by my desires. The desires themselves play a background role. The foreground is the goal I have in focus, namely, to win respect.

So says Pettit, and I think he is absolutely right. Is decision theory guilty of confusing goals with explanations, foreground with background? No doubt some theorists are guilty. But that is because they misunderstand, or misapply, the theory. Frank Ramsey and Leonard Savage never suggested that we should aim at utility. And Luce and Raiffa specifically warn against the idea that a person might prefer one option to another because the first has a higher expected utility.8 Does decision theory give any practical advice at all? Only a weak sort, I think. It counsels a sort of coherence or consistency in preference. Conform your preferences to these constraints, it says. If you obey, then you needn't worry about maximizing your expected utility. That will take care of itself, as a matter of mathematical necessity.9

That sort of advice is not very helpful, and it doesn't say much of anything on the subject of how we reason about preferences ina most of ordinary life. So it would speak in favor of the assumption of deliberative structure if it could add something illuminating. And on first blush, it does. Something seems right about the idea that when we make decisions, we consider and aim at some feature of an outcome, something about it that makes it seem to us worth while. As Pettit puts it,




"when in ordinary practice an agent comes to prefer one option to alternatives, he often prefers it for a property other than answering in a certain way to his prospect-desires; say, for the property of being an obligation of etiquette, being amusing, or being in the public interest." If he were to aim at utility, then "he would be concerned in every decision with realizing the property of best satisfying his prospect-preferences, rather than with realizing independent properties like those of being mannerly, having fun, or advancing the common good." [213-214]

But it is unclear what the assumption of desiderative structure is supposed to have to do with this point. Granted, when we form preferences and make decisions, we do not nor should we aim at utility, or at the satisfaction of our preferences. Rather, we do and should aim at the bearers of utility, and at those things that will (as a matter of fact) satisfy our preferences most fully. But what has this to do with the question of whether prospects or properties are the basic objects of desire and preference? If I am concerned with realizing independent properties like being mannerly or advancing the common good, isn't that just another way of saying that I am concerned with the independent prospect that I be mannerly, with the objective outcome that the common good be advanced? You will be true to your own best values by aiming at the property rather than the "one off" property of having well satisfied desires, but just as true by aiming at the prospects themselves. What is the advantage, then, of the assumption of desiderative structure? None that I can see.

In any case, the practical advice here is not very practical. When I am having trouble deciding what to do, it may be of some minimal help to be told that I should keep the various properties or outcomes I care about in view, but the help is only minimal. I conclude that there is little support for the assumption of desiderative structure to be found in considerations of practicality.

(iii) Non-autonomous. Pettit argues that decision theory needs some account of how options are to be individuated, in light of some interesting and compelling examples. He then



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argues that the assumption of desiderative structure provides the resources for individuating options properly. Decision theory without the assumption, then, is non-autonomous, in the sense that it needs help from a principle that it does not contain.

It is on this score that I find Pettit's story most convincing. The examples certainly do show that decision theory needs some kind of substantive criterion for individuating outcomes and prospects, and the idea that the properties instantiated in (and by) the outcomes are the key seems awfully attractive. I have been tempted by it myself.'0 Still, the same structural worries that have occupied my criticisms so far return to haunt Pettit's positive suggestion.

The simplest illustration of the issue of outcome individuation is what I'll call the Hostess Example. Consider three cases. In case one, your hostess offers you a plate of fruit containing a large apple and a small orange, asking you to choose one leaving the other for her. You choose the apple. In case two, the choice is between a small apple and an orange, and you choose the orange (you are quite hungry). In case three, you choose between a large apple and a small apple, and this time it strikes you as rude and greedy to pick the larger apple, so you take the small one. In each case, you chose the option you preferred. But then, it seems, you prefer Large Apple to Orange, Orange to Small Apple, and Small Apple to Large Apple, and this collection of preferences violates transitivity, an axiom of decision theory.

Of course, you can insist, with perfect justice, that your preferences are transitive after all. Had you chosen the Large Apple in case three, the outcome would have been significantly different from what it would have been had you chosen the Large Apple in case one, even though in each case you would end up with the same piece of fruit. Fruit isn't everything. Manners are important, too. In case one, the outcome could properly be described as, "I get a large apple", but in case three it must be described as "I get a large apple by displaying bad manners". If these outcomes are different, then your preferences do not violate transitivity. And, they are different. So you are still coherent.




The problem, though, is that the two outcomes, "I get a large apple" and "I get a large apple by displaying bad manners" are individuated here not by their intrinsic features, but rather by their alternatives. Taking the larger apple displays bad manners in virtue of the alternative's being the smaller apple. Now, if we adopt the general rule of always individuating outcomes by (among other things) their alternatives, then the constraint of transitivity will become vacuous. No set of preferences could fail to display it, even in principle. For whenever somebody prefers A to B, B to C, and C to A (that is, whenever transitivity appears to fail), we will have to say that the A in the first preference is really A-when-the-alternative-was-B, whereas in the third preference the A is really A-when-the-alternative-is-C. Call those AB and Ac, respectively. So the real preferences are AB to B, B to C, and C to AC. No problem with transitivity there. This problem, "pulling the teeth" from the axioms by individuating outcomes by their alternatives, shows up in examinations of other axioms of decision theory, too, as Pettit explains in his paper. So the theory faces the threat of toothlessness.

Pettit's suggestion, attractive on its face, is to say that outcomes are to be considered distinct just in case the agent herself cares about a property that distinguishes them. In the Hostess Example, you do in fact care about manners, so the fact that one apple-acquisition is rude and the other not rude is sufficient to distinguish the outcomes; that the individuation is by reference to the alternatives is not really the point. By contrast, if I told you in some other context that I preferred an apple to a banana, a banana to a cantaloupe, and a cantaloupe to an apple, you might ask me how this could be. If there is no property I care about to distinguish either the two A-outcomes, or the two B-outcomes, or the two C-outcomes, then I am not saved from incoherence by the fact that one theoretically could distinguish them by their alternatives. The bare difference is not a relevant difference until it is one that I care about. Pettit puts it like this:

If it [the assumption of desiderative structure] is sound, then we should individuate outcomes and options so as to respect the principle that if any two token options or outcomes differ in respect of a desired property then,



216 J. DREIER

regardless of how similar they are otherwise, they should be counted as different. [166]

Attractive as this idea seems to me, I am afraid it is no help to decision theory, so the assumption of desiderative structure gains no real support from it. The reason emerges when we begin to think about just what desiring and preferring properties amounts to. Here is Pettit's official explanation:

To desire a prospect is to prefer it to the prospects that you think of as the alternatives. To desire a property is to be disposed to prefer a prospect that has it, assuming that there is only one, among a set of prospects that otherwise leave you indifferent. [199]

Plug this explanation into the principle for individuating outcomes, and we find that that principle amounts to:

Individuation by Properties Count two outcomes as different if they differ by some property whose possession makes a difference in the agent's preferences among prospects.

But now compare that principle to

Individuation by Prospects Count two outcomes as different if the agent prefers one to the other.

How can these two principles come apart? How can they disagree on any cases? As far as I can see, there is only one way. It could happen that some pair of outcomes might differ by some property that matters to the agent, even though the agent is in the particular instance indifferent between them. That might happen because the prospects differ by two or more properties that as it happens balance. For instance, our gracious guest might find that the rudeness of taking the larger apple was outweighed if the larger apple were also chocolate-covered. In the right context, and with the right sort of chocolate, the properties could balance and reach the indifference point. In that case, Individuation by Properties would still imply that the two outcomes describable as "taking the large apple" are different, while Individuation by Prospects would not. But this is a minor difference. Individuation by Prospects doesn't imply that the two large apple takings are not different, and anyway




examples in which different outcomes get treated the same because the agent is indifferent between them do not seem to pose any problems for decision theory.

Pettit has definitely put his finger on a problem: the problem of individuating outcomes. If outcomes are individuated always in part by their alternatives, then the constraints of decision theory will lose all of their teeth. We've seen how transitivity is defanged, but Pettit shows that another axiom, independence, runs into a similar problem, and indeed almost all of them will be emptied of content in the same way. The suggested solution was to individuate outcomes by their properties, counting outcomes as distinct if they differ by properties that the agent cares about. I argued that this suggestion was no better than individuating outcomes directly by the agent's preferences: count them as different if the agent prefers one to the other. Is this a plausible solution? That depends on how one understands the notion of preference.

Individuation by Prospects is threatened by any behavioristic conception of preference, including a simplistic functionalism. Suppose preferring one thing to another is just being disposed to choose the first when presented with the choice between it and the second. When someone prefers A to B, B to C, and C to A, the question of whether her preferences are transitive amounts to the question of whether she prefers Ac to AB. But there is no disposition to choose between Ac and AB, since there is no possible situation in which one would face the choice between A-when-the-alternative-is-C and A-when-the-alternative-is-B. Now it is tempting to say that Individuation by Properties can help at this point, since it directs our attention to an interesting property: rudeness, for instance. True, I cannot be presented with the choice between having a large apple without being rude and having a large apple but being rude in taking it, but nevertheless I can simply ask myself which I prefer.' And I can answer that question easily, since I do in fact care about rudeness and I know that I do.

All this is quite right, but the real point is that we have a clear enough idea of preference even in cases where there could be no corresponding disposition. The important thing is to



218 J. DREIER

abandon the behaviorism tied up in decision theory's roots; whether we think of preferences as having properties for objects or prospects isn't going to matter.

NOTES

Or desire. Pettit suggests that we think of desiring a certain state of affairs as simply preferring it to the complement state of affairs. So, desiring that the sun shine tomorrow is simply preferring that the sun shine tomorrow to that it not shine tomorrow. I'll follow his suggestion here.

2 "Decision Theory as Folk Psychology", p. 197. This paper is the main subject of the present one, and hereafter all references to it are in square brackets in the main body of the text.

3 At least this is so according to the conception of propositions and states of affairs at work here, namely, that they are (indexed by) sets of possible worlds. In the text, I say that nearly every proposition can be pressed into the something has the property F form. The exception is the proposition, if there is one, that nothing at all exists.

4 In classical logic, 3x(Fx V Gx) is equivalent to 3xFx V 3yGy, so restricting the special class of propositions to include existentially quantified disjunctions but not disjunctions of existentially quantified formulas is no restriction.

5 To be clear: when I want to move to the new city, that is not for the sake of 'fulfilling another desire', but rather for the sake of being near my family. It is probably best to think of the 'for the sake of as taking the contents of the desires as its relata. That certain contents stand in that relation from my point of view is made true by the fact that I desire things as I do.

6 But note that this is an artifact of the (popular and philosophically compelling) model of possible worlds. As Pettit notes, in Richard Jeffrey's theory there are no atoms other than the impossible proposition (Jeffrey, 1983, esp pp. 147-149). The point here is that the question of whether there are any atoms is not answered by decision theory per se, but may have different answers in different versions of the theory. Of course, metaphysical or logical considerations external to decision theory may well persuade us one way or the other.

7 See the previous note. I might add that a similar idea to Pettit's might be generated' even without the assumption of atoms. Instead of supposing that

there are absolutely basic preferences for atoms, we might suppose that each prospect has its utility or place in the preference ordering grounded in the utility or place in the ordering of its subprospects. Though the grounding never actually reaches any ground floor, so we wouldn't find any 'basic' preferences, there would nevertheless be a kind of relative basicness in the




picture. This relative basicness seems to me exactly as attractive, and exactly as unattractive, as the absolute basicness that shows up in the atomist picture.

8 See (Luce and Raiffa, 1957) 31-2, where this mistake is the first in a list of common fallacies.

9 I argue further for this conception of the advice offered by decision theory in Dreier (1996). 10 In Dreier (1996).

It seems to me that Richard Jeffrey's evidentiary decision theory may be in better shape at this point than the causal versions new and old, since for him the fundamental objects of preference are news items, as he sometimes puts it. So Jeffrey could put the question to me this way. Suppose you know that you had taken the large apple, he might say, but you've forgotten under what circumstances. You ask your wife to remind you, and she is now about to tell you whether the alternative to the large apple was the small apple or the orange. Which news item do you hope to hear? (See Jeffrey, 1983), especially pp. 82-83.

REFERENCES

Dreier, J. (1996): 'Rational Preference: Decision Theory as a Theory of Practical Rationality', Theory and Decision 40(3), 249-276.

Jeffrey, R. (1983): The Logic of Decision, 2nd edn., Chicago: University of Chicago.

Luce, R.D. and H. Raiffa (1957): Games and Decisions, New York: Dover Books.

Pettit, P. and M. Smith (1990): 'Backgrounding desire', Philosophical Review 99, 565-592.

Ramsey, F. (1926): 'Truth and Probability', reprinted in F. Ramsey, Foundations, D.H. Mellor (ed.), London: Routledge, 1978.

Savage, L.J. (1954): The Foundations of Statistics, New York: John Wiley.

Department of Philosophy Brown University P.O. Box 1918 Providence RI 02912 USA



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DOI 10. 1007/s 1 1098-004-4917-7 J. DREIER · DOI 10. 1007/s 1 1098-004-4917-7 J. DREIER ... So my critical discussion is offered in the spirit loyal ... Theory benefits by taking