Joint action and spontaneity

This paper poses a challenge to theories of joint action. In addition to the typical requirement of explaining how agents count as acting together as opposed to acting in parallel or independently—the togetherness requirement—it is argued that theories must explain how agents can be spontaneously joined such that they can act together spontaneously—the spontaneity requirement. To be spontaneously joined is to be immediately joined. The challenge arises because the typical means of satisfying the togetherness requirement, for example, planning, expressing willingness, and so forth, are forms of mediating, binding interaction and so seem to eliminate the possibility of spontaneity. Likewise, taking spontaneity seriously makes it difficult to see how the togetherness requirement can be simultaneously met. The challenge threatens the very idea of joint agency.