Abstract: Competent action in the world of people entails having the concept of a person and knowing how people behave. Much of this is implicit. The psychologist’s job is to make this knowledge explicit, coherent, and systematic. But what knowledge is required to manage social life? (A corresponding question: what must an adequate psychology account for?) Descriptive Psychology’s Person Concept approaches this question by pre-empirically starting with: 1) People make sense. 2) People are what they are and not something else instead. And, 4) Don’t count on people being simpler than they have to be. Implicit is the base-line expectation that people are intentional and cognizant actors able to deliberate about theirs and others behavior. This understanding, compatible with ordinary meanings of action and responsibility, is made explicit through a systematic unpacking of the Person Concept’s formulation of behavior as Intentional Action. This is accomplished through a Parametric Analysis of intentional action consisting of 1) an Actor, 2) what the actor Wants to accomplish, 3) what the actor Knows or distinguishes in the circumstance relevant to what the actor Wants, 4) what the actor Knows-How to do, 5) the real time Performance of the action, 6) the action’s Achievement, 7) the action’s Significance and, 8) the Personal Characteristics expressed by the action. These eight parameters are expandable and locate how any behavior is alike or different from any other. This analysis provides the teacher and clinician both a checklist of behavioral constituents, and, when relevant content is absent, where to look.