Shared intention and personal intentions

Margaret Gilbert 0 0 M. Gilbert (&) Department of Philosophy, University of California at Irvine , 625 Mesa Road, Irvine, CA 92697-4555, USA This article explores the question: what is it for two or more people to intend to do something in the future? In a technical phrase, what is it for people to share an intention? Extending and refining earlier work of the author's, it argues for three criteria of adequacy for an account of shared intention (the disjunction, concurrence, and obligation criteria) and offers an account that satisfies them. According to this account, in technical terms explained in the paper, people share an intention when and only when they are jointly committed to intend as a body to do such-and-such in the future. This account is compared and contrasted with the common approach that treats shared intention as a matter of personal intentions, with particular reference to the work of Michael Bratman. 1 Introduction In this paper I discuss a phenomenon I shall refer to as shared intention. I first addressed the topic in What is it for Us to Intend?, having prepared the ground for it in On Social Facts, where my focus was on acting together and shared readiness to act.1 In later work I have amplified many aspects of the discussion.2 The present paper pulls together central elements of this material, while extending and clarifying 1 Gilbert (1997, 1989). Also Gilbert (1990). 2 For example Gilbert (2003, 2006, Chaps. 6 and 7). it in various ways.3 It also compares and contrasts my approach to shared intention with another, common one that treats shared intention as a matter of personal intentions, with particular attention to the work of Michael Bratman. 2 Shared intention The technical phrase shared intention, now in common use by philosophers, comes from Bratman.4 It is best to specify how I shall understand it here. As elsewhere in this paper, for the sake of simplicity I refer to an example involving two people.5 Suppose Alice asks Ben What are you doing this afternoon? and Ben, gesturing towards Celia, replies Were going shopping. If Alice were improbablyto respond I see: you intend to go shopping and Celia intends to go shopping, Ben might irritably reply No, no: we intend to go shopping! In this paper I construe the phrase shared intention roughly as follows: a shared intention is what people refer to whenas in Bens case they utter everyday sentences of the form We intend to do A, Were going to do A, and the like, and are not using them elliptically for We both intend to do A or We all intend to do A, and so on.6 I shall refer to such sentences, when used to refer to a shared intention, as shared intention sentences. Shared intention sentences can take a variety of forms. For example, instead of taking the form We intend to do A they may take the form Our intention is to do A. They may also take the form We intend that p as does We (Diane and Ed) intend that Fern attend the best school in town. I focus here on the intend to form of shared intention sentences. Shared intention sentences mayexplicitly or implicitlyrefer to particular individuals as such as parties to the shared intention. Or they may refer to individuals insofar as they possess certain general features including relational features. Again for the sake of simplicity, my focus in this article is on the former kind of shared intention sentence, and the corresponding shared intentions.7 3 Special features of this discussion in relation to Gilbert (1997) include: an explicit focus on future directed shared intentions; emphasis on the problems three plausible criteria of adequacy pose for an account of shared intention in terms of corresponding personal intentions; expansion of my previous argument for the disjunction criterion; a further articulation of the obligation criterion, and further discussion of the ability of a plural subject or joint commitment account to satisfy it (see the text below for explanation of technical terms used in this note). 4 See Bratman (1993). 5 Cf. Bratman (1993). My perspective on shared intention has no problem with larger scale cases. Gilbert (2006, Chap. 8.3) discusses a broader range of phenomena but its general approach can be applied to the case of shared intention. 6 Equally appropriate phrases that have been used in the literature are collective intention and joint intention. 7 My perspective on shared intention can accommodate cases involving populations individuated by one or more common features, something that is necessary when dealing with what Scott Shapiro has referred to as massively shared intentions, that is, the shared intentions of very large populations. On this see Gilbert (2006, Chap. 8.3). I am here concerned with shared intentions that regard the future, rather than shared intentions in acting. In at least some cases of future-directed intentions, whether shared or not, it is natural also to speak of plans. I take it that, indeed, if one plans to do something in the future, then one intends to do it in the sense of intention pertinent here.8 Intuitively an appropriate agreement between the parties is sufficient to bring a shared intention into being. Suppose that one morning Gina says to Harry Shall we go to the library this afternoon? and Harry replies Sure. Without further ado, Gina might now properly say to a third party, of Harry and herself, We intend to go to the library this afternoon, in the shared intention sense of We intend In at least this kind of case one might also speak in terms of planning. Thus, in the example, Gina might equally well say to the third party We plan to go to the library this afternoon. A future-directed shared intention may arise without an agreement between the parties. Thus Isobel may tell Jake and Kirsten to go to London together. They may exchange glances of pleasure and begin working on the details of their trip. They have a shared intention to go to London together but have never made an agreement to do so. Clearly, though understanding agreements should help us to understand shared intention, understanding shared intention is not simply a matter of understanding agreements. 3 The personal intentions perspective Shared intention sentencesthough completely commonplacemay seem to raise a squarely philosophical puzzle. On the face of it, one who says, for instance, Larry and Meg intend to paint the living room tomorrow ascribes an intention to Larry and Meg, as opposed to Larry, on the one hand, and Meg, on the other. One may think that this cannot be rightthings cannot be as they seem. One may think this because one assumes that the only intentions in the human domain are intentions of single human beings as opposed to intentions of two or more human beings, such as the putative intention of Larry and Meg. Perhaps one makes this assumption because one thinks that only a being with some feature possessed by single human beings and not possessed by two or more human bein (...truncated)