In his early thought (which for our purposes will be considered to be roughly the time period from his first post World War I lecture course in 1919 to the publication of Being and Time in 1927), Heidegger offers a rich description of our practical engagement with the world. The aim of this project is to develop a Heideggerian conception of action from these early, concrete descriptions of the practical dimension of human life. The central feature of this Heideggerian conception of action is that action is understood as involving interdependent aspects of passivity and activity (or receptivity and spontaneity, in a more Kantian formulation). Considered in its entirety, my dissertation provides what I take to be a fruitful interpretation of Heidegger's early thought from the standpoint of his understanding of action. It also provides the provisional basis and framework for the further development of a general conception of human agency that can be extended beyond Heidegger's thought.