With this volume we present 24 contributions to the philosophy of design. Design is an emerging topic in philosophy and not yet one on which work is shaped by a common set of questions or by an academically entrenched discipline of philosophy of design. We therefore consider it an effort in itself that we can present 24 contributions. Throughout the years we have approached in our careers design from our separate disciplinary perspectives and probed whether design was becoming a more general topic of philosophical reflection. One of us (Pieter) is working in a philosophy department and analyzed design as part of a larger project within the philosophy of technology. This has led to a predecessor volume on the philosophy of design (Vermaas et al. 2008), to analyses of design (Houkes and Vermaas 2010), to joint work with design researchers on the structure of design (e.g., Vermaas and Dorst 2007), and to the creation of the Design Research Foundations book series, in which this volume has appeared. The second of us (Stéphane) has worked first as a ‘philosophy applied to design’ teacher (Vial 2015c) and now is working in a design department and in a design research center. He analyzed design from a phenomenological perspective and contributed to developing the knowledge of design in France. These efforts led to a monograph about how to design affects, structures, and frames experience (Vial 2010) and to the founding of the French-speaking journal Sciences du Design edited by Stéphane (Vial 2017).