Economics from Shared Reality and Distinct Persons

Alice has flour and work available; Bob has a loaf. Their books both say that nothing is owed. Who can eat, what can they do together, and what must each preserve for the other? These questions have answers before prices or markets enter. A complete two-person economy identifies the information those answers require: each person's usable resources, recorded claims and outstanding agreements. Within the model, we prove that this description is necessary and sufficient for the stated future-action tests. The general condition is exact: every action a description reports must be possible from the actual situation it describes. With personal requirements and information retained, this preserves shared futures, ethical judgments and informed control. Relevant past effects require additional memory. Comparison-cost settlement has a unique minimizer at fixed net positions; specified accounting rules make it reachable. Physical measurements and the identification of experienced persons determine where these mathematical results apply.