Our planning agency contributes to our lives in fundamental ways. Prior partial plans settle practical questions about the future. They thereby pose problems of means, filter solutions to those problems, and guide action. This plan-infused background frames our practical thinking in ways that cohere with our resource limits and help organize our lives, both over time and socially. And these forms of practical thinking involve guidance by norms of plan rationality, including norms of plan consistency, means-end coherence, and stability over time.
But why are these norms of rationality? Would these norms be stable under a planning agent's reflection? I try to answer these questions in a way that responds to a skeptical challenge. While I highlight pragmatic reasons for being a planning agent, these need to be supplemented fully to explain the force of these norms in the particular case. I argue that the needed further rationale appeals to the idea that these norms track certain conditions of a planning agent's self-governance, both at a time and over time. With respect to diachronic plan rationality, this approach leads to a modest plan conservatism.