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Parallel Planning

A representation or plan is \emph{agent-neutral} if its content does not specify any particular agent or agents; a planning process is agent-neutral if it involves only agent-neutral representations.
Practical vs theoretical reasoning: ‘The mark of practical reasoning is that the thing wanted is \emph{at a distance} from the immediate action, and the immediate action is calculated as a way of getting or doing or securing the thing wanted’ \citep[p.\ 79]{Anscombe:1957ln}. See also \citet[p.\ 1]{millgram:2001_practical}: ‘Practical reasoning is reasoning directed towards action: figuring out what to do, as contrasted with figuring out how the facts stand.’
Some agents each \emph{individually make a plan for all the agents' actions} just if: there is an outcome; each agent individually, without discussion, communication or prior arrangement, plans for that outcome; and each agent’s plan specifies roles for herself and all the other agents.
Our planning is \emph{parallel} just if you and I are each planning actions that I will eventually perform and actions that you will eventually perform, where the resulting plans non-accidentally match.
Two or more plans \emph{match} just if they are the same, or similar enough that the differences don't matter in the following sense. First, for a particular agent's plan, let the \emph{self part} be those steps concerning what will be the agent's own actions and let the \emph{other part} be the other steps. Now consider what would happen if, for a particular agent, the other part of her plan were as nearly identical to the self part (or parts) of the other's plan (or others' plans) as psychologically possible. If the agent's self part would not be significantly different, let us say that any differences between her plan the other's (or others') are not relevant for her. Finally, if for some plans the differences are not relevant for any of the agents, then let us say that the differences don't matter.
The guiding idea behind Bratman's planning theory of shared intention is this: ’shared agency consists, at bottom, in interconnected planning agency of the participants’ (Bratman 2011, p. 11).

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

Facts about your plans feature in my plans & conversely.

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)

parallel planning

You plan our actions, yours and mine, and I plan our actions too

Here, interconnected planning is planning where facts about your plans feature in my plans & conversely. I think there are some cases for which interconnected planning just does not seem like a good approach.
Suppose you and I are tasked with moving this table through that door. In doing this, must my plan take into account facts about your intentions as well as about the weight of the table, width of the door &c? This case has some special features: (i) there is a single most salient route for the table given our objective; (ii) there is a single most salient way of dividing up the roles between us. I suggest that, in this situation, neither of us needs to form a plan involving the others' intentions. The situation makes this redundant. All we have to plan is how two people in our situations should move the table through the door.
To a first approximation, then, what the situation seems to call for is not that our plans are interconnected but rather that we each make a plan for the table-moving action as a whole. This is inspiration for the view that we might arrive at sufficient conditions by reflecting on parallel rather than interconnected planning ...

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

Facts about your plans feature in my plans & conversely.

parallel planning

You plan my actions as well as yours, and I do likewise.

So Bratman’s notion of interconnected planning seems not to fit this sort of case. (This is much as Schmid suggests.)
In parallel planning, I plan all of our actions and you do the same. I want to suggest that shared agency sometimes requires only parallel, and not interconnected planning.
Some of you are probably already thinking that the very idea of parallel planning is incoherent, and I will face up to this objection.
But first I want you to suspend disbelief and consider how parallel planning could enable us to coordinate our actions and our plans ...
Suppose you and I are parents about to change our baby's nappy.
the other’s actionschange nappyprepare babyprepare nappyplacestripcleanunfoldpositionassemble
This involves preparing the baby and preparing the nappy.
You're holding the baby and I'm nearest the pile of clean nappies, so there's a single most salient way of dividing the task between us.
Preparing the baby is, of course, a complex action ...
Now there are relational constraints on how the baby and nappy should be prepared; how you clean constrains and is constrained by how I prepare the clean nappy (because we don't want to get pooh on it).
\textbf{How do we meet these relational constraints?} The fact that I have a plan for the whole thing and so do you, and the fact that these plans are identical or similar enough that the differences don't matter means that your plan for your actions is constrained by your plan for my actions, which is my plan for my actions. So thanks to our parallel planning---to the fact that we each plan the whole action---your plan for your actions is indirectly constrained by my plan for my actions; and conversely. So: in parallel planning, we meet these relational constraints not by thinking about each other's intentions but by planning each other's actions.
There's just one tiny problem. In supposing that we both make a plan for the whole action, I'm implying, of course, that we each make plans for actions that are not our own. And this seems incoherent, unless perhaps we (the agents performing the action) are irrational or ignorant.
[Don’t say: messes up the two-phase approach below: It seems incoherent because the elements of plans we make are intentions; so, apparently, in making a plan for your action I would end up intending your actions. But I can't intend your actions, I suppose. What can we do?]

agent-neutral practical deliberation

I want to address this problem in two phases.
The first phase concerns practical deliberation. (Here I step back from planning and consider mere deliberation about what should be done [the distinction between practical reasoning and practical deliberation is mentioned in the notes above].) As Millgram says, ‘Practical reasoning is reasoning directed towards action: figuring out what to do, as contrasted with figuring out how the facts stand' \citet[p.\ 1]{millgram:2001_practical}.
I suggest that the reasoning which leads to action can be \emph{agent-neutral}; that is, it can avoid the specification of any particular agent or agents.
To illustrate, suppose that you're having some work done in your flat and have hired an electrician and a decorator. The decorator arrives first. Realising that she will need to work around the electrician, she needs to work out how the electrician will approach the job. Because the decorator is also a skilled electrician, she makes a plan for the re-wiring of your flat. This process of planning has the key features of practical reasoning: it is a matter of figuring out what to do, it involves determining means given ends, and it involves selecting means for various ends in such a way that all of the means can be implemented together.
Now you might say that what the decorator is doing is not really practical deliberation. But note that it is preparation for action. Suppose you find out that the electrician can't make it, so you ask the decorator to stand in as the electrician. She does not have to engage in further planning or practical reasoning; she is already poised to act. So the practical reasoning that she has already done for actions that were to be performed by someone other than her puts her in a position to act immediately.
(Even if you want to say, for some reason, that reasoning concerning actions one believes others will perform cannot be practical, you should recognise that it has some important features of practical reasoning: it serves to put one in a position to act, it involves determining means given ends, it involves selecting means for various ends that can all be implemented together, and it involves adopting a perspective insofar as particular agents' biases and quirks are ignored. These are the features of practical reasoning that matter for my argument.)
So it seems to me it should be uncontroversial that processes of practical deliberation can concern actions that you expect other to eventually perform, and that such practcical deliberation can lead directly to action if it later turns out that it is you who is to perform this action.
Note that in practical deliberation one has a special perspective on the actions; one illustration of this is that you ignore particular agents' biases and quirks, even if these are highly reliable. These can inform prediction but not planning processes. This will be important later.
Agent-neutral practical deliberation has practical applications in coordinating our actions. (Housemates pizza example: agree to make it but then have to leave immediately; shows that practical delibration can occur in parallel ...)

But what attitude results from practical deliberation?

That some of your practical reasoning concerns actions that others will eventually perform does not entail that you have practical attitudes towards their actions.
(Just here we have to be careful with terminology. I am claiming that the decorator makes a plan for actions she believes the electrician will eventually perform. I am not claiming that the decorator plans or intends to perform those actions. Note also that to say the decorator `has a plan' for goals she believes are not her responsibility may be misleading: she has beliefs about how these goals could be achieved (so has a plan in one sense) but she does not have intentions concerning these goals (so lacks a plan in another sense).)
If the agent-neutral plan is to result in me acting, then I need to have some sort of practical attitude towards it.
But since some of the actions it specifies are, I know, actions you will eventually perform, I can't simply intend to implement the plan.

not intention concerning own action;
and not mere belief, nor intention, that another acts

So here I seem to face a dilemma. [First horn: not intention] It seems that I can't intend it in the ordinary sense because then I'd be intending its parts, and some of its parts are actions that, I know, you will eventually perform. So, apparently, I'm blocked from intending the plan
[Second horn: not belief] On the other hand, if I merely entertain a belief about the plan --- if, for instance, I merely believe that the plan identifies a way we could achieve some goal --- then it's unclear how I could be acting on it at all.
What seems to happen in the case of the dectorator-turned-electrician is that the decorator starts out with beliefs and then, when asked to stand in for the electrician, ends up with intentions.

open-ended intentionsSecond phase: we need to appeal to some ways in which intentions can be open-ended.: whenIt's a familiar idea that intentions can be open-ended with respect to when something intended will be done. For instance, you can intend to visit Cafe Europa without intending to do so on any particular day., and whoIt's also true that intentions can be open-ended with respect to who will act on them.Consider a couple planning some tasks at the start of the weekend: they need to buy bread, to clean the bath, ... At this point, their intention is that one or both of them will do each of these things, but there is no further specification concerning who will act. Now you might say that you can't intend something without settling who will act. But this seems wrong given that (i) the couple's attitudes are practical, and (ii) generate requirements concerning agglommeration. (Even before it's determined who will do what, I know that I'm not going to be able to spend the afternoon in the pub.)[*skip] You might also say that open-ended intentions generate pressure to filling in details. This is true, but the details are not always filled by further intentions. At some point intentions give out and we just act. The point of appealing to the table-moving example was that here there is no need for the intention to specify the agents.I want to suggest that appeal to the open-endedness of intentions will help with the dilemma I had.The problem was, what attitude could I have to another's actions?

The attitude I can have is this: with respect to the whole plan, I intend that we implement it. And with respect to its components, I intend that you or I or we do them.
This seems almost but not quite satisfactory to me. The potential difficulty, I think, is with the idea that, concerning things that will eventually be your actions, I have an intention that is open-ended with respect to whether it is you, me or we who will do those things. This seems unsatisfactory because at some point I may know that you will do these things and I don’t have to concern myself with them; and this will free me to do things that would prevent me from performing actions that are essential for our success but which I know you will perform. By contrast, having an open-ended intention implies that there is still a possibility that I will act and that I am still bound by requirements on agglommeration.
While this appears to be a deficit of the account, I want to suggest that it is actually a virtue. In changing the nappy, I am always somewhat ready to take on part of your role; to grab the baby if you unexpectedly have a sneezeing attack, say. By contrast, when I am merely relying on knowledge about your future actions and planning my own actions in the light of this knowledge, we are not strictly acting as one. So my having intentions concerning actions that I expect you to perform where these intentions are open-ended with respect to who will act is a mark of acting as one. (Note: this applies to my own actions as well; I shouldn’t intend that I do them, but that I or you or we do them.)
the other’s actionschange nappyprepare babyprepare nappyplacestripcleanunfoldpositionassemble
So my intentions don't specify who will do what. But they don't need to, because this is already adqeuately specified by the fact that you're holding the baby and I'm nearest the clean nappies. So in this case what determines who does what are the constraints, not the intentions.

tennis doubles vs surgery

You might object (along lines Barry Smith did to a related idea) that parallel planning only makes sense where roles can be swapped. It is fine for tennis doubles, say, but disastrous for surgery where surgeon and nurse have quite different expertise.
But note that parallel planning doesn’t have to reach all the way down. You only have to plan the other’s actions in enough detail to coordinate with them. And of course parallel planning needn’t be---and typically isn’t---the only means by which coordination is achieved.
In general, parallel planning does not require that I plan all of the actions of all of the agents; it only requires that I plan those actions that constrain my own.
What matters is just this: in parallel planning, each agent has a plan which includes some actions that, if things go as they should, will be performed by other agents.

Parallel planning


Each agent individually plans not only her own actions but also those of others.

1. Parallel planning is agent-neutral.

2. Parallel planning results in intentions that are open-ended with respect to who will act.

shared intentional agency consists, at bottom, in interconnected planning agency of the participants.’

(Bratman 2011, p. 11)

Facts about your plans feature in my plans & conversely.

parallel planning

You plan my actions as well as yours, and I do likewise.

And parallel planning contrasts with interconnected planning.
This is why, despite appearances, I think the notion of parallel planning is coherent. Without irrationality or ignorance, it is possible for us each to plan all of our actions, yours and mine, and to act on these plans. In doing so we achieve coordination and manifest collective intentionality not by thinking about each other's plans but, more directly, by planning each other's actions.