This paper offers a theoretical analysis of Self-Determination Theory (SDT) and its claims regarding human autonomy. Self-determination theorists have advanced a form of self-regulated, engaged behavior (i.e., autonomy), founded upon on a consilient account of human motivation that assumes multiple, hierarchical levels of organization and causation (e.g., biological, psychological, and social). Autonomy, from this perspective, is taken to emerge from underlying biological mechanisms, but also able to exert its own causal effects in the world as a unique psychological phenomenon. We contend that in theorizing this way, self-determination theorists have invoked a mixed discourse of mechanism and autonomy that leaves important questions unanswered, perhaps most importantly those concerning how autonomy as a kind of volition can fit coherently in the mechanistic account of world that they advocate. We then offer an alternative perspective based upon the work of various hermeneutic-phenomenological thinkers in philosophy and psychology. This alternative perspective conceptualizes human phenomena such as autonomy and motivation in agentic terms, emphasizing meaningful participation in possibility-laden contexts of everyday practices.