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The Problem of Joint Action really is a problem. Does Bratman’s theory of shared intention solve it? (We don’t know yet; but at least we know what Bratman’s theory is.)

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Given the difficulties we found in identifying a quick answer to the The Problem of Joint Action (in Quick Answers Fail), it seems that we may need to posulate shared intention.

This is a problem. Everyone agrees that shared intentions stand to joint actions roughly as intentions stand to ordinary, individual actions.[1] Most also agree that shared intentions are neither shared nor intentions. But apart from that, there is much disagreement about what shared intentions are.

Some hold that the states in question involve a novel attitude (Searle, 1990; Gallotti & Frith, 2013). Others have explored the notion that the primary distinguishing feature of these states 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 perhaps the most fundamental distinguishing mark of these states is the way they arise, namely through team reasoning (Gold & Sugden, 2007; Pacherie, 2013). Opposing all such views, Bratman (1992); Bratman (2014) argues that the distinctive states, which he calls `shared intentions', can be realised by multiple ordinary individual intentions and other attitudes whose contents interlock in a distinctive way. Bratman’s approach has inspired a family of accounts along broadly these lines, including Asarnow (2020), Blomberg (2016), Ludwig (2007); Ludwig (2016) and Tollefsen (2005).

How are we to determine when any two of these accounts should be regarded as competing attempts to characterise a single phenomenon and when they should be regarded as compatible attempts to characterise different phenomena? And how are we to single out, from among all of these accounts, those which are correct? The growing number and increasing diversity of accounts make urgent these twin problems. It may be that they can be solved. But a quick glance at the history of philosophy suggests not.

Postulating shared intention should therefore be a last resort.[2]

But if you are forced to postulate shared intention, it is essential to be familiar with the leading, most carefully developed account of it: Bratman on Shared Intentional Action.

Is Bratman’s account ‘a model [...] that can support wide-ranging research in philosophy and the social sciences’ (Bratman, 2022, p. 8)? If not, is there a better alternative?

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dual-process theory of instrumental action : Instrumental action ‘is controlled by two dissociable processes: a goal-directed and an habitual process’ (Dickinson, 2016, p. 177). (See instrumental action.)
joint action : Many of the things we do are, or could be, done with others. Mundane examples favoured by philosophers include painting a house together (Bratman, 1992), lifting a heavy sofa together (Velleman, 1997), preparing a hollandaise sauce together (Searle, 1990), going to Chicago together (Kutz, 2000), and walking together (Gilbert, 1990). These examples are supposed to be paradigm cases of a class of phenomena we shall call ‘joint actions’.
Researchers have used a variety of labels including ‘joint action’ (Brooks, 1981; Sebanz, Bekkering, & Knoblich, 2006; Knoblich, Butterfill, & Sebanz, 2011; Tollefsen, 2005; Pettit & Schweikard, 2006; Carpenter, 2009; Pacherie, 2010; Brownell, 2011; Sacheli, Arcangeli, & Paulesu, 2018; Meyer, Wel, & Hunnius, 2013), ‘social action’ (Tuomela & Miller, 1985), ‘collective action’ (Searle, 1990; Gilbert, 2010), ‘joint activity’ (Baier, 1997), ‘acting together’ (Tuomela, 2000), ‘shared intentional activity’ (Bratman, 1997), ‘plural action’ (Schmid, 2008), ‘joint agency’ (Pacherie, 2013), ‘small scale shared agency’ (Bratman, 2014), ‘intentional joint action’ (Blomberg, 2016), ‘collective intentional behavior’ (Ludwig, 2016), and ‘collective activity’ (Longworth, 2019).
We leave open whether these are all labels for a single phenomenon or whether different researchers are targeting different things. As we use ‘joint action’, the term applies to everything any of these labels applies to.
problem : a question that is difficult to answer.
shared intention : An attitude that stands to joint action as ordinary, individual intention stands to ordinary, individual action. It is hard to find consensus on what shared intention is, but most agree that it is neither shared nor intention. (Variously called ‘collective’, ‘we-’ and ‘joint’ intention.)
The Problem of Joint Action : What distinguishes doing something jointly with another person from acting in parallel with them but merely side by side?


Asarnow, S. (2020). Shared Agency Without Shared Intention. The Philosophical Quarterly, forthcoming.
Baier, A. C. (1997). Doing Things With Others: The Mental Commons. In L. Alanen, S. Heinamaa, & T. Wallgren (Eds.), Commonality and particularity in ethics (pp. 15–44). Palgrave Macmillan.
Blomberg, O. (2016). Common Knowledge and Reductionism about Shared Agency. Australasian Journal of Philosophy, 94(2), 315–326.
Bratman, M. E. (1992). Shared cooperative activity. The Philosophical Review, 101(2), 327–341.
Bratman, M. E. (1997). I intend that we J. In R. Tuomela & G. Holmstrom-Hintikka (Eds.), Contemporary action theory, volume 2: Social action. Dordrecht: Kluwer.
Bratman, M. E. (2014). Shared agency: A planning theory of acting together. Oxford: Oxford University Press. Retrieved from
Bratman, M. E. (2022). A Planning Theory of Acting Together. Journal of the American Philosophical Association, 8(3), 1–8.
Brooks, D. H. M. (1981). Joint action. Mind, 90(357), 113–119. Retrieved from
Brownell, C. A. (2011). Early Developments in Joint Action. Review of Philosophy and Psychology, 2, 193–211.
Carpenter, M. (2009). Just how joint is joint action in infancy? Topics in Cognitive Science, 1(2), 380–392.
Dickinson, A. (2016). Instrumental conditioning revisited: Updating dual-process theory. In J. B. Trobalon & V. D. Chamizo (Eds.), Associative learning and cognition (Vol. 51, pp. 177–195). Edicions Universitat Barcelona.
Gallotti, M., & Frith, C. D. (2013). Social cognition in the we-mode. Trends in Cognitive Sciences, 17(4), 160–165.
Gilbert, M. P. (1990). Walking together: A paradigmatic social phenomenon. Midwest Studies in Philosophy, 15, 1–14.
Gilbert, M. P. (1992). On social facts. Princeton, NJ: Princeton University Press.
Gilbert, M. P. (2010). Collective action. In T. O’Connor & C. Sandis (Eds.), A companion to the philosophy of action (pp. 67–73). Oxford: Blackwell.
Gold, N., & Sugden, R. (2007). Collective intentions and team agency. Journal of Philosophy, 104(3), 109–137.
Helm, B. W. (2008). Plural agents. Nous, 42(1), 17–49.
Knoblich, G., Butterfill, S. A., & Sebanz, N. (2011). Psychological research on joint action: Theory and data. In B. Ross (Ed.), Psychology of learning and motivation (Vol. 51, pp. 59–101). San Diego, CA: Academic Press.
Kutz, C. (2000). Acting together. Philosophy and Phenomenological Research, 61(1), 1–31.
Longworth, G. (2019). Sharing non-observational knowledge. Inquiry, 0(0), 1–21.
Ludwig, K. (2007). Collective intentional behavior from the standpoint of semantics. Nous, 41(3), 355–393.
Ludwig, K. (2016). From Individual to Plural Agency: Collective Action. Oxford University Press.
Meyer, M., Wel, R. P. R. D. van der, & Hunnius, S. (2013). Higher-order action planning for individual and joint object manipulations. Experimental Brain Research, 225(4), 579–588.
Pacherie, E. (2010). The phenomenology of joint action: Self-agency vs. Joint-agency. In A. Seemann (Ed.), Joint action. MIT Press.
Pacherie, E. (2013). Intentional joint agency: Shared intention lite. Synthese, 190(10), 1817–1839.
Pettit, P., & Schweikard, D. (2006). Joint Actions and Group Agents. Philosophy of the Social Sciences, 36(1), 18–39.
Roth, A. S. (2004). Shared agency and contralateral commitments. The Philosophical Review, 113(3), 359–410.
Sacheli, L. M., Arcangeli, E., & Paulesu, E. (2018). Evidence for a dyadic motor plan in joint action. Scientific Reports, 8(1), 5027.
Schmid, H. B. (2008). Plural action. Philosophy of the Social Sciences, 38(1), 25–54.
Searle, J. R. (1990). Collective intentions and actions. In P. Cohen, J. Morgan, & M. E. Pollack (Eds.), Intentions in communication (pp. 90–105). Cambridge: Cambridge University Press.
Sebanz, N., Bekkering, H., & Knoblich, G. (2006). Joint action: Bodies and mind moving together. Trends in Cognitive Sciences, 10(2), 70–76.
Sebanz, N., Knoblich, G., & Prinz, W. (2005). How two share a task: Corepresenting stimulus-response mappings. Journal of Experimental Psychology: Human Perception and Performance, 31(6), 1234–1246.
Tollefsen, D. (2005). Let’s pretend: Children and joint action. Philosophy of the Social Sciences, 35(75), 74–97.
Tuomela, R. (2000). Cooperation: A Philosophical Study. Dordrecht: Springer.
Tuomela, R., & Miller, K. (1985). We-Intentions and Social Action. Analyse & Kritik, 7(1), 26–43.
Velleman, D. (1997). How to share an intention. Philosophy and Phenomenological Research, 57(1), 29–50.


  1. As you may remember (from The Problem of Action meets Habitual Processes), reflection on the dual-process theory of instrumental action suggests that most philosophers are wrong about how intentions stand to ordinary, individual actions. (Incidentally, there may even be an analogous consideration concerning joint action: what Sebanz, Knoblich, & Prinz (2005) call ‘task co-representation’ is, essentially, a stimlus--action mapping where the mapped action involves your action and mine.) ↩︎

  2. Again, the joint seems parallel to the individual in this respect: there are grounds for the view that postulating intention should be a last resort too. ↩︎