Christopher Alexander on design patterns and principles

This chapter offers an account of Christopher Alexander's notions of design patterns and principles. He pioneered the design pattern approach while being sceptical of design principles. The main contribution of this chapter is the exploration of the Alexandrian background to design patterns. In addition to his writings, the chapter relies on branches of philosophy of science to account for patterns. The aim of the chapter is to clarify and motivate the design pattern approach in the way I argue it was intended by Alexander and later practised in the field of software development. In addition to the contrast between design patterns and principles, the notion of forces and the epistemology of patterns are explored. The discussion of principles in ethics shares with educational design principles the purpose of giving action guidance. Both in design and ethics, I see a tension between the generality of principles and the particularities of any given application. Relying on discussions in political philosophy, I separate three forms of context sensitivity—a key theme in both fields: Methodological, theoretical, and application-wise, and briefly discuss the problem of critical distance for educational design: How can theory offer a critical perspective if facts about the context enter theory-formation?