This paper is concerned with the problem of self-identification in the domain of action. We claim that this problem can arise not just for the self as object, but also for the self as subject in the ascription of agency. We discuss and evaluate some proposals concerning the mechanisms involved in self-identification and in agencyascription, and their possible impairments in pathological cases. We argue in favor of a simulation hypothesis that claims that actions, whether overt or covert, are centrally simulated by the neural network, and that this simulation provides the basis for action recognition and attribution.In this paper we will be concerned with the problem of self-identification as it arises in the domain of action, which we will take to include both overt and covert or simulated actions.Talk of a problem of identification presupposes a contrast set, and the possibility that, in seeking to identify one self, one picks out something in the contrast set instead. With self-identification, two contrast sets must be considered: the world at large and the set of other selves. The problem of self-identification therefore divides into two sub-problems: self-world discrimination and self-other discrimination. We focus here on the latter problem. Our first aim is to show that there is a problem of self-other discrimination. Our second aim is to discuss and evaluate some proposals concerning the mechanisms involved in self-identification and in agencyascription, and their possible impairments in pathological cases.In the first section, we will examine some of the reasons why philosophers have paid little attention to the problem of self-other discrimination, and investigate the conditions under which this problem can arise. In section 2, we will concentrate on the identification of the self as a physical body. In section 3, we will present evidence that we are able to perceive the intentions of others. This will involve the idea of shared representations of actions, the nature and format of which we willWe would like to thank Tim Bayne, Jérôme Dokic, Pierre Jacob, Joëlle Proust, Komarine Romdenh-Romluc, and the participants at the Workshop on Simulation held in Paris in May 2003 for discussions and comments on earlier versions of this paper. We are especially indebted to Gregory Currie for his penetrating and helpful comments and suggestions on multiple drafts of this paper.