The leading, best developed account of shared intention is due to Michael Bratman. What are the main features of his account?
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What distinguishes joint actions from parallel but merely individual actions?
Bratman’s first step towards answering this question is to postulate 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)
The view that joint action involves shared intention is almost universal.1 To illustrate:
‘I take a collective action to involve a collective [shared] intention.’ (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)
‘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)
‘Shared intentionality is the foundation upon which joint action is built.’ (Carpenter, 2009, p. 381)
Once we postulate shared intention, the key problem becomes to say what it is.
Bratman’s theory has two components, a functional characterisation and a substantial ‘construction of interconnected intentions and other related attitudes … that would … play the roles characteristic of shared intention’ (Bratman, 2014, p. 32).2
Shared intention serves to (i) coordinate activities, (ii) coordinate planning, and (iii) structure bargaining.
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.
Bratman also proposes a requirement: shared intentions should be inferentially and normatively integrated with ordinary, individual intentions.
Bratman claims that the following are collectively sufficient3 conditions for you and I to have a shared intention that we J:
(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 (1a), (1b), and meshing subplans of (1a) and (1b); you intend that we J in accordance with and because of (1a), (1b), and meshing subplans of (1a) and (1b)
(3) (1) and (2) are common knowledge between us.’ (Bratman, 1993, p. View 4)
Elaborating on the intention in condition (2), Bratman adds that each agent must intend ‘that the route from these intentions to our joint activity satisfies the connection condition’ (Bratman, 2014, p. 52). But what is the connection condition? It is ‘the condition that specifies the nature of [the] explanatory relation’ between shared intention and joint action … [T]he 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, pp. 78–9).
In more recent work Bratman has added these further conditions to those above:
(4) The persistence of each intention in conditions (1) and (2) is interdependent with the persistence of every other such intention (Bratman, 1997, p. 153; Bratman, 2006, pp. 7–8; Bratman, 2009, p. 157; Bratman, 2010, p. 12; Bratman, 2014, p. 65).
The common knowledge condition, (3) above, is extended to include these further conditions, (4) and (5).
On this course, I shall usually simplify exposition by discussing conditions (1)–(3) only. However, conditions (4) and (5) will be relevant (and explained) in Two (Failed?) Objections to Bratman.
There are some further developments of the view in Bratman’s most recent work (Bratman, 2014).
This course focusses on Bratman’s theory because it is the best developed, most influential and has yet to encounter a successful objection in print (despite many attempts).
You are not expected to study alternatives to Bratman’s theory on this course. But you may choose to do so.
Opposing Bratman’s view that shared intention does not require any ontological, metaphysical or conceptual innovations, some hold that shared intentions involve a novel attitude (Searle, 1990; Gallotti & Frith, 2013). Others have explored the notion that the primary distinguishing feature of shared intentions is not the kind of attitude involved but rather the kind of subject, which is plural (Helm, 2008). Or they may differ from ordinary intentions in involving distinctive obligations or commitments to others (Gilbert, 1992; Roth, 2004). Or the most fundamental distinguishing mark of shared intentions is the way they arise, namely through team reasoning (Gold & Sugden, 2007; Pacherie, 2012)—a view that we will return to later in the course when considering game theory.
Your question will normally be answered in the question session associated with this lecture.
In Bratman (1992), the following were offered as jointly sufficient and individually necessary conditions; the retreat to sufficient conditions occurs in Bratman (1997, pp. 143–4) where he notes that ‘for all that I have said, shared intention might be multiply realizable.’ ↩