What is design? Definitions range from design as a product or process of thinking, modelling or problem solving, to all-encompassing visions of design as the transformation of social environments. Some definitions of design stress the aspect of function, others the similarity with art. Even if we try to break down the definition to design objects in the sense of designed material artefacts such as chairs, books or buildings, defining their essential properties proves difficult. What is the special ingredient that makes an artefact a design object? Based on the philosophical method of conceptual analysis, the present chapter asserts that any definition of design objects necessarily includes their appearance. Since the creation of appearance and aesthetic experience is an essential task of design, the study of aesthetics should consider design among its paramount subjects. This argumentation leads to an astonishing conclusion for traditional philosophy: The philosophical divide between ontology and aesthetics is bridged when it comes to design objects.