One of the most ignored problems in the philosophy of collective intentionality and action is the question of identity. But what happens when the composition of a group changes during the action process? Can we say that it is the same group that develops an intention and performs the corresponding action, if the persons that make up the group initially are different from those who complete the action? For making the problem clear, let me take an example of the sort used by Bratman or Tuomela, two prominent philosophers in this field:
A group of four movers intends to carry a piano to an apartment on the sixth floor of an apartment building. On the staircase to the second floor, one mover gets a whiplash, so a colleague is called up in order to replace him. On the staircase to the third floor, one of the three original movers hurts his back and he is also replaced by a colleague. On the stairs to the fourth floor one of the remaining original removers slips and sprains his ankle and is replaced as well. And the last man of the original group has to be replaced on the fifth floor because he seriously hurts his knee. So in the end four different men put the piano on its place in the apartment on the sixth floor.Some readers will recognize here the old philosophical problem called “The Ship of Theseus”: When Theseus returns from Crete to Athens, after having killed the Minotaur, he has to repair his ship at sea and he replaces the old planks of the ship one by one by new ones so that finally none of the old planks of the ship that left Crete remains. Then the question is: Is the ship that arrives in Athens the same one as the ship that sailed from Crete? Or for our example: Is the group that arrived at the sixth floor the same group as the group that started to carry the piano upstairs? If you say no, the idea of group intention has to be skipped, for the consequence is that only individual intentions and actions are possible. But this conflicts with many facts that support the view that collectivities do exist and act. For instance, parliaments vote down a motion, hockey teams become world champion and armies wage wars. However, if you say yes, you have saved the idea of group intention but then you have to explain how it is possible that a group can have an intention even if in the end no member of the original group remains. You have also to explain what it means that a group keeps having an intention, although a group mind (brain) doesn’t exist and although the original group members that have taken up the intention no longer have this intention. Or you have to explain what it means that a group acts, although it is the individual members who move their limbs (for it’s John who kicks a goal with his leg and not the “team”). Unless you give up the idea that the analysis of group actions is analogous to the analysis of individual actions (as Tuomela thinks, for instance; see his The Philosophy of Sociality, chapter 5).