The concept of agency, although central to many sociological debates, has remained frustratingly elusive to pin down. This article is an attempt to open up what has been called the "black box" of personal agency by distinguishing clearly between two contrasting conceptions of the phenomenon. These two conceptions are very apparent in the manner in which the concept is defined in sociological reference works, resembling as it does a similar contrast in the treatment of the concept of power. The two (...) are referred to as type 1 and type 2 or the power of agency as compared with agentic power, the essential contrast being that the first refers to an actor's ability to initiate and maintain a program of action while the second refers to an actor's ability to act independently of the constraining power of social structure. The nature of these two forms of personal agency is then illustrated by referring to material taken from Weber's essay The Protestant Ethic and the Spirit of Capitalism, this essay itself being understood as an argument that focuses on the crucial role played by an increase in the power of agency in ushering in the modern world. Finally, it is argued that these two conceptions of agency possess no given logical relationship with each other, it being perfectly possible for individuals to be possessed of considerable power of agency while lacking agentic power, and vice versa. It is therefore concluded that it is important, in all discussions of human agency, to distinguish clearly between these two forms. (shrink)