In this chapter, the author presents a conceptual framework for early-stage interaction design (EDOS) together with a method for embedding conceptual artifacts in user interfaces. The notion of ‘externalized design’ from postmodern architecture is used as an analogy for how to incorporate conceptual artifacts like social ideas in user interfaces. This is proposed as a new approach to theory-based design in human-computer interaction (HCI) and computer-supported collaborative learning (CSCL). The framework is applied to the retrospective analysis of two interactive systems the author has been involved in designing over a number of years. These systems were stimulated by two concepts associated with American pragmatism (generalized other, reflection-in-action). A multistage process for expressing the concepts in user interfaces is presented. The chapter ends by discussing the strengths and limitations of the EDOS framework, comparing it with related work, and suggesting directions for further work.