As shown in this handbook, there is a variety of positions and practices in Designwissenschaft. Various understandings of design and of Wissenschaft logically lead to different understandings of Designwissenschaft and subsequently the practice of hypothesizing. A discussion on hypotheses should be mindful of this diversity. Pluralistic but fragmented, for better or worse, are the characteristics of Designwissenschaft. Given this situation, I intend to discuss hypothesis in ways to support a Designwissenschaft that retains the tradition of Design, fits contemporary knowledge production, and fuses with the best Wissenschaft can offer. Through the discussion of hypothesis in scientific and design inquiry, the fusion of Design and Wissenschaft: Designwissenschaft is highlighted.