Coherent sociotechnical systems do not emerge from accumulation but from composition. This chapter synthesizes the architectural framework of Purpose Driven Design, demonstrating how the nine constructs—Purpose, Value, Function, Process, Structure, Order, Culture, Memory, and Storage—form an integrated system that enables clarity, accountability, and adaptive evolution. It reframes architecture not as the assembly of components, but as the disciplined composition of design surfaces that remain intelligible under conditions of scale and change. The chapter highlights the consequences of misalignment, the role of coherence as a design objective, and the necessity of continuous stewardship in sustaining system integrity. It concludes by positioning the unit as the primary architectural form through which purpose, responsibility, and adaptability can be realized, offering a foundation for designing systems that remain meaningful, governable, and resilient over time.