This chapter surveys some recent philosophical and empirical work on the nature and structure of action, on conscious agency, and on our knowledge of actions. By reuniting the causal approach with the rational approach, the causalists opened the way for a naturalistic stance in action theory and thus for an integration of philosophical and scientific enquiries. Many philosophers introduce a conception of intentions as distinctive, sui generis, mental states. Intentions are responsible for triggering or initiating the intended action (initiating function) and for guiding its course until completion. Dual-intention theories provide a partial answer to the problem of causal deviance. The chapter concentrates on the functional architecture of motor cognition, introducing some of the theoretical concepts, models, and hypotheses that play a central role in current thinking in the motor domain and are of particular relevance for philosophical theorizing on action.