Persons or selves do not merely perceive their world – they also act upon it intentionally. Indeed, the self's capacities for perception and action are inseparably intertwined, even if these capacities may be exercised independently on some occasions. For example, a person incapable of voluntary self-movement cannot spontaneously generate the kind of motion parallax which, as we saw in the previous chapter, is vital to extracting information about the spatial structure of his environment from the light energies encountered by his eyes. And a person incapable of self-perception is deprived of the information feedback necessary for executing fine-grained movements of her limbs. In this chapter I shall be arguing that there must exist a class of mental acts corresponding to the traditional notion of a volition or act of will, and that any human action properly described as voluntary must involve the occurrence of at least one such mental act. Volitions, I maintain, play an indispensable causal role in the genesis of voluntary bodily movement, a role for which mental states like belief and desire are constitutionally unsuited, even though states of the latter sort are indeed normally to be included amongst the causal antecedents of volitions. Volitions are different from states like belief and desire not only in respect of their distinctive causal role, but also in respect of their distinctive intentional content, which, as we shall see, always has an ineliminably self-referential character.

1. AGENTS AND ACTIONS

Let me begin by introducing some basic terminology and explaining the theoretical framework I mean to deploy. In what follows I shall, at least to start with, be using the terms agent and action in very broad senses.