Research by design refers to the design of architectural research as an integral part of architectural design processes. In 1980s, it emerged as a third way in design research that was dominated until then by the methods of natural sciences and humanities. With this new formulation of design research, a methodological and epistemological transformation occurs, leading to the integration of practical knowledge into architectural research. The primary epistemological question transforms from knowing what design is and knowing how to design to knowing what through the act of design. The integration of the act of design in research transforms the status of design in design research from being an object of inquiry to being a research approach. In the literature on research by design, this transformation is often related with Donald Sch&ouml / n&rsquo / s conceptualization of &ldquo / reflective practice.&rdquo / The main discussion of reflective practice is primarily methodological rather than epistemological. Although it provides methodological insights, it is not sufficient to constitute an epistemological basis for research by design. Thus, the epistemological basis of research by design has not yet been adequately defined. In this study, the notion of &ldquo / reflective practice&rdquo / is investigated in a broader context relating it to its sources in the concepts of &ldquo / tacit knowledge&rdquo / and &ldquo / action research.&rdquo / A conceptual framework for research by design is constructed by relating these concepts with the discussions on research by design and with practical philosophy, the implications of which has remained rather uninvestigated in this context. Aristotle&rsquo / s elaboration of knowledge generation in action and the concept of phron&amp / #275 / sis (practical knowledge, prudence, or practical wisdom) constitute the underpinning of this conceptual framework. The conceptual framework that is constructed on the basis of the key concepts in practical philosophy is discussed in the context of architectural design education. When architectural design education is formulated as a process of research by design within this framework, knowledge generated in the educational design processes promises not only to improve the particular educational context and architectural education but eventually to contribute to architectural knowledge.