Design is increasingly becoming a part of the university curriculum and research agenda. A theory about the pro-cess and practice of design might be important to estab-lish design as a main subject at universities. We believe it is in the interest of many design communities – not least the Participatory Design (PD) community – to engage in theorizing design, on the basis of our understanding of design and design practices. This theory could be posi-tioned as an alternative to other attempts to theorize design, for example the influential efforts of the Information Systems (IS) community. We urge the PD community to engage in collective theory building, and we present a framework intended to support our shared reflections on the design of human technologies.