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Bratman on Shared Intentional Action

Recall our question, What distinguishes joint actions from parallel but merely individual actions?

shared intention

‘A first step is to say that what distinguishes you and me from you and the Stranger is that you and I share an intention to walk together—we (you and I) intend to walk together—but you and the Stranger do not. In modest sociality, joint activity is explained by such a shared intention; whereas no such explanation is available for the combined activity of you and the Stranger. This does not, however, get us very far; for we do not yet know what a shared intention is, and how it connects up with joint action’ (Bratman, 2009, p. 152).

‘A first step is to say that what distinguishes’ the sisters cycling together from the strangers cycling side by side is that the sisters to cycle together ... but the strangers do not.

‘This does not, however, get us very far; for we do not yet know what a is’

Bratman, 2009 p. 152

Lots of philosophers and some psychologists think that all joint actions involve shared intention, and even that characterising joint action is fundamentally a matter of characterising shared intention.

‘I take a collective action to involve a collective [shared] intention.’

(Gilbert, 2006, p. 5)

(Gilbert 2006, p. 5)

‘The sine qua non of collaborative action is a joint goal [shared intention] and a joint commitment’

(Tomasello, 2008, p. 181)

(Tomasello 2008, p. 181)

‘the key property of joint action lies in its internal component [...] in the participants’ having a “collective” or “shared” intention.’

(Alonso, 2009, pp. 444--5)

(Alonso 2009, pp. 444-5)

‘Shared intentionality is the foundation upon which joint action is built.’

(Carpenter, 2009, p. 381)

(Carpenter 2009, p. 381)


shared intention

‘shared’ 1 : Ayesha and her best friend have the same haircut

-> the Simple Theory

‘shared’ 2 : Ayesha and her brother share a mother

-> plural subject account (Schmid, Helm)

Let’s try to understand, in really minimal terms, what the plural subject account is saying ...
For comparison, properties like mass and volume can have plural subjects.

e.g. our volume, yours and mine, is approx 130 litres.

cf. our intention, yours and mine, is that we paint the house.

On a view like Bratman’s, shared intentions are not shared. They are also not intentions.

‘shared’ 3: The group shares a wheelbarrow

-> aggregate (or ‘group’) agent (Pettit, Gold & Sugden)

Be careful not to confuse plural and group agents.
Do you understand the three distinct senses of shared?
I was asking what it is. So far only negative characterisation: neither shared nor an intention.


shared intention

- not shared; not intention

What is shared intention?

Functional characterisation:

shared intention serves to (a) coordinate activities,
(b) coordinate planning, and
(c) structure bargaining


Inferential integration... and normative integration (e.g. agglomeration)

Substantial account:

To illustrate: if we share an intention that we cook dinner, this shared intention will (iii) structure bargaining insofar as we may need to decide what to cook or how to cook it on the assumption that we are cooking it together; the shared intention will also require us to (ii) coordinate our planning by each bringing complementary ingredients and tools, and to (i) coordinate our activities by preparing the ingredients in the right order.
The functional characterisation is really important: if we accept it, then it tells a lot about what shared intentions could and could not be. In particular, it either rules out Searle’s account or at least shows that the account is not clearly an account of shared intention because it does not explain how the attitude Searle characterises, the ‘we-intention’ could coordinate activities, coordinate planning and structure bargaining.
inferential integration ... [illustrate with planning example where you have to plan both individual and joint action]
normative integration (e.g. agglommeration)
[illustrate agglomeration for individual case first, then joint]
These points are extremely simple but also extremely powerful. They are powerful because they create problems for many approaches to shared agency. Consider Searle’s view again. He thinks that shared intentions are not intentions but a new, sui generis kind of attitude (which is why he uses the term ‘we-intentions’). If you think this, you have to explain how come the new attitudes are inferentially and normatively integrated with ordinary intentions. (I’m not saying this can’t be done, just that doing it is challenging, and certainly not something that Searle has attempted as far as I know.)
We’ll shortly see how the substantial account is built step by step. But maybe it’s helpful to mention the strategy
the construction ...

step 1

‘Our shared intention to paint together involves your intention that we paint and my intention that we paint.’

Bratman (2015, p. 12)

(Bratman, 2014, p. 12)

(Compare the Simple Theory)

This is roughly what the Simple Theory said This might seem completely innocuous, but it is interestingly controversial.

the ‘mafia case’* motivates ... and painting the house different colours motivates ...

step 2

We each intend that we paint by way of the intentions that we paint* and by meshing* subplans of these intentions.

Given what I said earlier, I don’t think the mafia case actually motivates step 2. But I did provide other cases (the Tarantino walkers and blocking the asile) which do seem to motivate step 2.
star: complication ‘and that the route from these intentions to our joint activity satisfies the connection condition’ (Bratman, 2014, p. 52).
On the connection condition: It is ‘the condition that specifies the nature of [the] explanatory relation’ between shared intention and joint action (Bratman, 2014, p. 78).. ‘the basic idea is that what is central to the connection condition is that each is responsive to the intentions and actions of the other in ways that track the intended end of the joint action--where all this is out in the open.’ (Bratman, 2014, p. 79).
We intend to paint the house, but I blue and you red. Earlier work: I trick you ... In the book: ‘we have a problem. In a case of shared intention we will normally try to resolve that problem by making adjustments in one or both of these sub-plans, perhaps by way of bargaining, in the direction of co-possibility. So we want our construction to account for is standard social­ norm-responsive functioning of the shared intention.’ (Bratman, n.d., p. 53)
meshing subplans are required
star: meshing
‘The sub-plans of the participants \emph{mesh} when it is possible that all of these sub-plans taken to­ gether be successfully executed.’ (Bratman, 2014, p. 53)
So much for step 2; now we come to the last major step (I’m skipping some details.)


step 3

‘there is common knowledge among the participants of the conditions cited in this construction’

Bratman (2015, p. 58)

(Bratman, 2014, p. 58)
Why impose the common knowledge condition? Before discussing this [I might have to skip discussion of this, but there is a useful quote on the handout], let me provide a summary of where we are with Bratman’s account.
Why require common knowledge in the construction of shared intention? ‘in shared intention the fact of the shared intention will normally be out in the open: there will be public access to the fact of shared intention. Such public access to the shared intention will normally be involved in further thought that is characteristic of shared intention, as when we plan together how to carry out our shared intention. Since such shared planning about how to carry out our shared intention is part of the normal functioning of that shared intention, we need an element in our construction of shared intention whose functioning supports some such thinking of each about our shared intention.’ (Bratman, 2014, p. 57)

What is shared intention?

Functional characterisation:

shared intention serves to (a) coordinate activities, (b) coordinate planning and (c) structure bargaining


Inferential integration... and normative integration (e.g. agglomeration)

Substantial account:

We have a shared intention that we J if

‘1. (a) I intend that we J and (b) you intend that we J

‘2. I intend that we J in accordance with and because of la, lb, and meshing subplans of la and lb; you intend [likewise] …

‘3. 1 and 2 are common knowledge between us’

(Bratman 1993: View 4)

These are the conditions that we have been discussing.
Note that these conditions are offered as sufficient but not necessary. (Bratman originally claimed that they were necessary and sufficient, but nothing in the construction rules out alternative realisations of the functional characterisation of shared intention.)
Are sufficient conditions sufficient for achieving Bratman’s aims? Bratman’s pitch is this. Recall the continuity thesis (‘once God created individual planning agents and ... they have relevant knowledge of each other’s minds, nothing fundamentally new--conceptually, metaphysically, or normatively--needs to be added for there to be modest sociality.’ p.8) Bratman reasons that if we can give sufficient conditions for shared agency that are consistent with the continuity thesis, then our default assumption should be that shared agency does not require concepual, metaphysical or normative innovation.
So if we accept Bratman’s sufficient conditions, then we should also accept the continuity thesis. (There might issues about whether merely sufficient conditions are enough to fulfil his aim of providing a framework for theorising about shared agency; more on this when we come to consider joint action and development.)


What distinguishes joint actions from parallel but merely individual actions?


Any account of shared agency must draw a line between joint actions and parallel but merely individual actions.


Theoretical framework for psychology and formal models.

So Bratman provides a candidate answer to the question.
Does the candidate answer avoid counterexamples?
And does Bratman’s candidate answer meet our aim of providing a theoretical framework that can help us in investigating for psychology and formal models? (I guess we will see later how useful it is, when we come to the psychological discoveries and formal models.)
Bratman’s theory answers question, so meets requirement and takes us towards the aim.

short essay question:

Why, if at all, do we need a theory of shared intention?

(Will be a while before this question makes sense.)

plan d’attaque

premise: Shared intention can only be understood as the solution to a problem.

1. What is the Problem of Joint Action?

2. Can we solve the Problem without shared intention?

3. If we do need shared intention, what is the best account available?