Agent probabilities & Agent probabilities & free willfree will

Helen BeebeeHelen Beebee

University of BirminghamUniversity of Birmingham

Hand-wavy introductionHand-wavy introductionSome features of the world that we care about don’t Some features of the world that we care about don’t exist according to the ‘view from nowhere’:exist according to the ‘view from nowhere’:

colourscolours free willfree will moral responsibility.moral responsibility.

But:But:

It would be an error to infer that we are are mistaken It would be an error to infer that we are are mistaken when we make positive claims about these things.when we make positive claims about these things.

Such claims are made from our own perspective; that Such claims are made from our own perspective; that perspective can’t be eliminated without loss of perspective can’t be eliminated without loss of meaning.meaning.

The point of this talk is …The point of this talk is …… … to use (something like) Price’s notion of an ‘agent to use (something like) Price’s notion of an ‘agent probability’ in an attempt to characterise this probability’ in an attempt to characterise this perspective, so that:perspective, so that:

it is ‘up to us’ what we decide to do, orit is ‘up to us’ what we decide to do, ordifferent possible decisions are available to usdifferent possible decisions are available to us

whether or not determinism is true.whether or not determinism is true.

Main issue (cf. David’s talk): Main issue (cf. David’s talk): Our actions Our actions aren’t aren’t independent of prior states. So how should we independent of prior states. So how should we conceive of agent probabilities? conceive of agent probabilities?

Answer:Answer: As an expression of the agent’s perspective As an expression of the agent’s perspective (not as either degrees of belief or fictions).(not as either degrees of belief or fictions).

Two problems for compatibilistsTwo problems for compatibilists

► Consequence Argument:Consequence Argument: Determinism is Determinism is incompatible with the ability to do otherwise, and incompatible with the ability to do otherwise, and so incompatible with free will.so incompatible with free will.

► Ginet’s epistemological argument: Ginet’s epistemological argument: If decisions If decisions were deterministically caused, it would be were deterministically caused, it would be conceptually possible for S to know what she was conceptually possible for S to know what she was going to decide before deciding. But it is going to decide before deciding. But it is conceptually impossible for someone to deliberate conceptually impossible for someone to deliberate when they already know what the outcome would when they already know what the outcome would be. So decisions cannot be deterministically caused.be. So decisions cannot be deterministically caused.

Evidential decision theoryEvidential decision theory

Coco knows:Coco knows: eating chocolate (C) is correlated with migraines eating chocolate (C) is correlated with migraines

(M)(M) but both C and M are caused by a ‘pre-but both C and M are caused by a ‘pre-

migrainous state’ (PMS)migrainous state’ (PMS)

Coco should go ahead and eat the Mars Bar. But it Coco should go ahead and eat the Mars Bar. But it looks like, for him, Pr(M/C)>Pr(M/~C), so EDT looks like, for him, Pr(M/C)>Pr(M/~C), so EDT recommends that he desist. BADrecommends that he desist. BAD. [2-3]. [2-3]

Need to find a way of screening off the correlation Need to find a way of screening off the correlation between C and PMS, to get the answer that Coco between C and PMS, to get the answer that Coco should eat the chocolate. How to do it?should eat the chocolate. How to do it?

Price’s solution:Price’s solution:

In conceiving of himself as genuinely deliberating In conceiving of himself as genuinely deliberating about what to do, Coco must regard himself as about what to do, Coco must regard himself as someone to whom the correlation between PMS someone to whom the correlation between PMS and C does not apply.and C does not apply.

The very fact that Coco (regards himself as The very fact that Coco (regards himself as being) free to do C or not, on the basis of being) free to do C or not, on the basis of deliberation about what to do, absents him from deliberation about what to do, absents him from the reference class for whose members eating the reference class for whose members eating chocolate increases Pr(PMS) and so Pr(M)chocolate increases Pr(PMS) and so Pr(M). [3]. [3]

Hitchcock’s twistHitchcock’s twistGives a formal characterisation of how APs are to be Gives a formal characterisation of how APs are to be

assigned. assigned.

The ‘disinterested probability distribution’ (DPD) The ‘disinterested probability distribution’ (DPD) represents Coco’s degrees of belief concerning the represents Coco’s degrees of belief concerning the actions/outcomes/background factors for his twin. actions/outcomes/background factors for his twin. [4/1][4/1]

The ‘fictional probability distribution’ (FPD) is as close The ‘fictional probability distribution’ (FPD) is as close to this as possible to this as possible exceptexcept that it makes Coco’s that it makes Coco’s possible actions probabilistically independent of possible actions probabilistically independent of background factors. background factors.

Coco uses the FDP in deciding what to do. Coco uses the FDP in deciding what to do. [4/2] [4/2]

A disagreement between Price A disagreement between Price & Hitchcock& Hitchcock

Price thinks Coco’s APs are ‘conditional Price thinks Coco’s APs are ‘conditional credences’: there really is some reference credences’: there really is some reference class of which Coco is a member (so Coco class of which Coco is a member (so Coco believes) within which there is no correlation believes) within which there is no correlation between PMS and C.between PMS and C.

Hitchcock appears to disagree: Coco’s APs are Hitchcock appears to disagree: Coco’s APs are not not his ‘degrees of belief about [his] own his ‘degrees of belief about [his] own actions, when assessed in a disinterested actions, when assessed in a disinterested and non-self-deceptive way’. Those are and non-self-deceptive way’. Those are given by the DPD, not the FPD. given by the DPD, not the FPD.

A problem for PriceA problem for Price

Coco might well Coco might well know know that there is some DPD that that there is some DPD that really does describe his situation.really does describe his situation.

E.g. next time he’s thinking about chocolate, he’ll know E.g. next time he’s thinking about chocolate, he’ll know that most people in his situation (people who wthat most people in his situation (people who wanant t chocolate and are rational) will take the chocolate chocolate and are rational) will take the chocolate (because it’s the rational thing to do). But his FPD (because it’s the rational thing to do). But his FPD must must differ from this or he won’t be able to conceive differ from this or he won’t be able to conceive himself as deliberating. (Cf. David’s talk.)himself as deliberating. (Cf. David’s talk.)

So perhaps we should go with Hitchcock and think of So perhaps we should go with Hitchcock and think of AAPPs as ‘fictional’? s as ‘fictional’?

Two problems for HitchcockTwo problems for Hitchcock

‘‘Deliberation requires the assumption of a freedom of Deliberation requires the assumption of a freedom of action that may, as a matter of fact, not exist’ (i.e. the action that may, as a matter of fact, not exist’ (i.e. the FPD really is, or might be, fictional).FPD really is, or might be, fictional).

So a So a freefree decision would be one where the DPD (and not decision would be one where the DPD (and not just the FPD) makes the possible actions just the FPD) makes the possible actions probabilistically independent of background factors. probabilistically independent of background factors.

(a) That’s a (a) That’s a very very strong requirement on freedom (pretty strong requirement on freedom (pretty much Ginet’s acausalism). much Ginet’s acausalism). [5][5]

(b) what (b) what justifies justifies my ignoring something I know about my ignoring something I know about myself (i.e. using the FPD and not the DPD)? How can myself (i.e. using the FPD and not the DPD)? How can it be rational to ignore a piece of relevant it be rational to ignore a piece of relevant information?information?

The story so far …The story so far …Both Price and Hitchcock take the notion of agent Both Price and Hitchcock take the notion of agent

probability to be bound up with the notion of probability to be bound up with the notion of freedom: to conceive of oneself as genuinely freedom: to conceive of oneself as genuinely deliberating, and so genuinely having a choice deliberating, and so genuinely having a choice between different options, one has to regard the between different options, one has to regard the outcome of deliberation as probabilistically outcome of deliberation as probabilistically independent of prior factors. independent of prior factors.

Price thinks this ‘regarding’ is a matter of having a Price thinks this ‘regarding’ is a matter of having a straightforwardly true belief (problematic). straightforwardly true belief (problematic).

Hitchcock thinks the ‘regarding’ is a matter of self-Hitchcock thinks the ‘regarding’ is a matter of self-deception, (also problematic). deception, (also problematic).

Solution:Solution:Agree with Hitchcock that APs don’t correspond Agree with Hitchcock that APs don’t correspond

to a real reference class of which the agent is to a real reference class of which the agent is a member ...a member ...

… … but disagree about what ‘free’ decision but disagree about what ‘free’ decision requires. APs are not ‘fictional’ but requires. APs are not ‘fictional’ but perspectival.perspectival.

APs don’t correspond to degrees of belief or APs don’t correspond to degrees of belief or statistical correlations, but are a probabilistic statistical correlations, but are a probabilistic expression of the agent’s perspective, i.e. her expression of the agent’s perspective, i.e. her perspective perspective as a deliberator.as a deliberator.

A Ginet-esque dilemmaA Ginet-esque dilemma

I’m a two-boxer. I know this because I know that in a Newcomb I’m a two-boxer. I know this because I know that in a Newcomb situation I’d deliberate and do what I think is the rational thing, viz situation I’d deliberate and do what I think is the rational thing, viz (so I believe), take both. Now put me in the Newcomb situation. (so I believe), take both. Now put me in the Newcomb situation. What do I do? What do I do?

It seems I can’t take myself to know I’ll take both, It seems I can’t take myself to know I’ll take both, andand simultaneously simultaneously regard myself as genuinely deliberating. regard myself as genuinely deliberating.

So eitherSo either

(a) I don’t know what I’ll do (but I (a) I don’t know what I’ll do (but I dodo know!), or know!), or

(b) I do know, in which case I can’t deliberate (but that knowledge is based (b) I do know, in which case I can’t deliberate (but that knowledge is based on the assumption that I will, in fact, deliberate!)on the assumption that I will, in fact, deliberate!)

Solution: Deliberation requires adopting the ‘deliberative Solution: Deliberation requires adopting the ‘deliberative perspective’, and this just IS the deployment of Aperspective’, and this just IS the deployment of APPs. In adopting s. In adopting the deliberative perspective I don’t deceive myself (I really am the deliberative perspective I don’t deceive myself (I really am deliberating!). I legitimately set aside knowledge I really do have deliberating!). I legitimately set aside knowledge I really do have –– legitimately because, again, that is part and parcel of the legitimately because, again, that is part and parcel of the deliberative perspective.deliberative perspective.

‘‘Could have done otherwise’Could have done otherwise’

APs deliver a sense in which different possible APs deliver a sense in which different possible decisions are available to me.decisions are available to me.

To be able to do otherwise just IS to adopt the To be able to do otherwise just IS to adopt the agent’s perspective, i.e. to adopt APs.agent’s perspective, i.e. to adopt APs.

More than one decision is open to me, and More than one decision is open to me, and open in a way that is unconstrained, open in a way that is unconstrained, from from my perspective as a deliberatormy perspective as a deliberator, by prior , by prior states. states. [8][8]

Some virtues of the storySome virtues of the story

► Unlike many compatibilist attempts to characterise Unlike many compatibilist attempts to characterise ‘CHDO’, it isn’t completely ad hoc. We need APs ‘CHDO’, it isn’t completely ad hoc. We need APs anyway (if Pricean EDT is right) for decision-theoretic anyway (if Pricean EDT is right) for decision-theoretic reasons, whether or not determinism is true. And that reasons, whether or not determinism is true. And that demands a story about why it’s OK to use them, demands a story about why it’s OK to use them, given that in general FPDs and DPD come apart.given that in general FPDs and DPD come apart.

► It locates free will where it should be: in the It locates free will where it should be: in the deliberation of agents about what to do. (This deliberation of agents about what to do. (This contrasts with libertarianism, which requires that free contrasts with libertarianism, which requires that free agents have the ability to behave like idiots. This is agents have the ability to behave like idiots. This is an odd power to want to have.)an odd power to want to have.)

The Consequence Argument …The Consequence Argument …

… … is invalid. is invalid.

There is There is a a sense of ‘CHDO’ that is sense of ‘CHDO’ that is incompatible with determinism. But this is incompatible with determinism. But this is not a sense of ‘CHDO’ that is legitimately not a sense of ‘CHDO’ that is legitimately applied by agents to their own deliberative applied by agents to their own deliberative situation: it is a sense of ‘CHDO’ that ignores situation: it is a sense of ‘CHDO’ that ignores the agent’s perspective.the agent’s perspective.

Ginet’s Epistemological ArgumentGinet’s Epistemological Argument

If decisions were deterministically caused, it would be If decisions were deterministically caused, it would be conceptually possible for S to know what she was conceptually possible for S to know what she was going to decide before deciding. But it is going to decide before deciding. But it is conceptually impossible for S to deliberate when conceptually impossible for S to deliberate when she already knows what the outcome would be. So she already knows what the outcome would be. So decisions cannot be deterministically caused.decisions cannot be deterministically caused.

(Actually the argument works just as well against (Actually the argument works just as well against libertarianism, agent-causalism, etc., assuming libertarianism, agent-causalism, etc., assuming either it’s CP that God knows what I’m going to do either it’s CP that God knows what I’m going to do or that time travel is CP.)or that time travel is CP.)

Solution:Solution:Ginet’s argument turns on the claim that it’s Ginet’s argument turns on the claim that it’s

conceptually impossible to decide to do something conceptually impossible to decide to do something when you already know what your decision will be.when you already know what your decision will be.

My story rejects this claim, while explaining why one My story rejects this claim, while explaining why one might be inclined to believe it:might be inclined to believe it:

You You cancan know what you’re going to decide, but know what you’re going to decide, but deliberation, i.e. the adoption of the agent’s deliberation, i.e. the adoption of the agent’s perspective, involves setting that knowledge aside. perspective, involves setting that knowledge aside. (You can’t deploy that knowledge in the process of (You can’t deploy that knowledge in the process of deliberation.)deliberation.)