Shared Intention and Bratman’s Maffia Cases
Suppose that you and I each intend that we go to New York together. Is this sufficient for us to have a shared intention? If we act on our intentions and succeed, will our going to New York constitute a shared intentional action, an action which is a consequence of our shared agency?
The general idea under consideration here is that two or more agents have a shared intention that they F just if each agent intends that they F.
Michael Bratman offers a counterexample. Suppose we elaborate the story so that your plan is to point a gun at me and bundle me into the boot (or trunk) of your car. Then you still intend that we go to New York together, but in a way that doesn’t depend on my intentions. As you see things, I’m going to New York with you whether I like it or not. This doesn’t seem like a case of shared intentional action. After all, it involves me being abducted. But it is still a case in which we each intend that we go to New York together and we do.
From this and other cases Bratman concludes that shared intention requires not only that we each intend that we go to New York together, but also that we do this by way of each other’s intentions and meshing subplans of those intentions. Is this the right conclusion to draw? I agree that our each having an intention that we go to New York togther cannot be sufficient for us to have a shared intention that we go to New York together. But does the counterexample really show that shared intention requires intentions about others’ intentions? I think not.
Let’s suppose for the sake of argument that only individuals can have intentions. So you and I cannot have an intention. At least not in anything like the sense in which we can have a bottle of wine or a parent, where one bottle (or parent) is both my parent and your parent. Intentions aren’t like this. None of your intentions are also mine, and none of my intentions are also yours. But the fact (if it is a fact) that intentions aren’t like this needn’t stop us from treating them as if they were.
What does it mean to treat an intention as if it could be an intention of two or more agents? Answering this question calls for a little background on intention. Intentions are characterised in part by norms which distinguish them from other attitudes like desire. For example, there is nothing wrong with having lots of different desires not all of which could be realised—to desire to be in two places at once, say. But when it comes to intention, it is not perfectly rational to have lots of intentions not all of which can be realised. Someone who intends to be in Chicago tomorrow probably shouldn’t also be intending to spend the whole day in New York.
Now in identifying norms characteristic of intention it is normal to consider only cases involving a single agent. But imagine for a moment that two or more agents could have one and the same intention. If that were possible, the norms characteristic of intention would have to be generalised from the single agent case to allow for multiple agents. For example, it would not be perfectly rational for *us* to have lots of intentions not all of which can be realised by *us*. Suppose that we intend to go to New York together but you intend to fly whereas I intend to drive. Then not all of our intentions can be realised. If we treat the first intention as our intention, then we are in a position to recognize that our having these intentions is not perfectly rational.
So what is wrong with the Maffia case where we each intend that we go to New York but your plan is to bundle me into the boot of your car at gunpoint? You implementing your plan is incompatible with me acting on my intention that we go to New York together. So our intentions are such that they cannot all be realised. If we took the intention that we go to New York together to be our intention, then we would be in a position to believe with justification that we are not being perfectly rational. So perhaps this is what is needed for us to have a shared intention: not intentions concerning each other’s intentions, but simply a disposition to treat an intention that we go to New York as if it were *our* intention.
In summary: (1) Maffia cases don’t show that shared intention requires intentions about others’ intentions; (2) to treat an intention that we F as *our* intention can be understood as treating it as subject to norms characteristic of intention where these have been generalised to cases involving multiple agents; (3) even if no intentions are had by more than one agent, it is still coherent to treat some as if they were; and (4) perhaps shared intention requires that each of us intends that we F and that each of us treats this intention as if it were our intention.
 The claim that intentions about others’ intentions are required for shared intention was weakened in later writing. But it remains true that Bratman’s only account of what realises shared intentions involves intentions about others’ intentions. My point here is that there may be other ways of realising shared intention.