Developing a widely accepted theory of behavior causation has been hampered by the lack of a rigorous approach to understanding the kinds of determinants at work. Interest in behavior change is also burgeoning, and requires a profound understanding of how personal and environmental determinants interact dynamically to predict changed behavioral outcomes. Behavior settings theory, a powerful naturalistic theory with a huge empirical underpinning, has long been available for describing the recurrent, everyday behavioral episodes in which many social and psychological scientists are interested. In this article, I review settings theory and update it in the light of a number of recent contributions from various quarters. I argue that this syncretic model should be seen as defining the proximate causal network surrounding these common behavioral episodes, which I call “situations.” I further propose that “contexts” should be thought of as the more distal, second-order causes circumscribing situations. I argue that these situational and contextual “spheres” of causation are a powerful way to understand behavior determination. I conclude by introducing a quasi-computational model of situations that is worthy of the further development necessary to make psychology a predictive science of behavioral causation and change.