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Aggregate Animals, Aggregate Subjects

On accounts like Bratman’s or Gilbert’s, ‘it makes some sense to say that the result is a kind of shared action: the individual people are, after all, acting intentionally throughout.

However, in a deeper sense, the activity is not shared: the group itself is not engaged in action whose aim the group finds worthwhile, and so the actions at issue here are merely those of individuals.

Thus, these accounts ... fail to make sense of a ... part of the landscape of social phenomena


Helm (2008, pp. 20-1)

Start with Helm’s challenge ([because I can answer it at the end]).
This is bad: who can explain what sharing amounts to? This is just a metaphor. Our problem is to discipline the metaphor, not to write as if we already understood it.
It is hard to understand what Helm is aiming for here, but I think the idea is that the actions should be not merely those of individuals but of the group itself.
The objection says something is missing, but actually our interest is driven by the thought that both Gilbert’s and Bratman’s approaches are inadqeuate as attempts to characterise shared agency.
How to make sense of this idea?


aggregate subject

I think Helm wants what I will call an ‘aggregate subject’. (He uses the term ‘plural robust agent’, but this is because he ignores a distinction between aggregate and plural subjects which will be important later.)
Meet an aggregate animal, the Portuguese man o' war (Physalia physalis), which is composed of polyps.
Here you can say that ‘the group [of polyps] itself’ is engaged in action which is not just a matter of the polyps all acting.
To illustrate, consider how it eats. Wikipedia: ‘Contractile cells in each tentacle drag the prey into range of the digestive polyps, the gastrozooids, which surround and digest the food by secreting enzymes that break down proteins, carbohydrates, and fats, while the gonozooids are responsible for reproduction.’
This jellyfish-like animal is a crude model for the sort of aggregate agent Helm (and others) suggest we need.
But how can such a thing exist? Humans do not mechanically attach themselves in the way that the polyps making up that jellyfish-like animal do.
So how are aggregate agents possible?

Gilbert: All joint commitments are commitments to emulate, as far as possible, a single body which does something (2013, p. 64).

In manifesting any collective phenomenon, we can truly say ‘We have created a third thing, and each of us is one of the parts’


Gilbert (2013, p. 269).

The collective value, belief or intention or whatever is primarily a value, belief or intention of this third thing.
What is this third thing?
I take it to be the single body we have emulated
in doing many things together, the point of doing them together is precisely not to emulate a single body: e.g. in lifting a table, or in foraging for berries, two bodies allow strategies that are impossible with just one body
Emulating as far as possible a single body that intends to wash up is not generally the most efficient way for several people to get the washing up done—Andrea and Heinrich had better exploit the fact that they are two than pretend to be an aggregate animal. The ‘emulating a single body’ form also seems to rule a shared intention to make out after washing up. And if it doesn’t preclude shared intentions to tango outright, it has unfortunate stylistic consequences in implying that those with such intentions are jointly committed to emulate a single body that intends to tango.
What is the motivation for this claim?
If, as Gilbert holds, joint commitments are all commitments to emulate a single body which does something, then the thing to which there is commitment involves nothing collective. Joint commitment thus serves, for Gilbert, as a device which transforms ordinary, singular phenomena (intention, belief or whatever) into collective phenomena with added commitments. To this extent Gilbert’s programme is reductionist: shared values, collective beliefs and the rest are reduced to joint commitments plus ordinary, individual values, beliefs and the rest.