This paper explores the importance of hope as a determining factor for patients to participate in first-in-human trials for synthetic biology therapies. This paper focuses on different aspects of hope in the context of human health and well-being and explores the varieties of hope expressed by patients. The research findings are based on interview data collected from stable gout and diabetes patients. Three concepts of hope have emerged from the interviews: hope as certainty ; hope as reflective uncertainty ; hope (...) as self-therapy. The purpose of the paper is twofold. First, it aims to underline the significance of hope in patients’ medical decision-making, as well as the beneficence of hope for patients’ well-being, and for progress in research. Second, it shows how philosophical investigations—in particular Descartes—explore the phenomenon of hope and provide medical empirical research with profitable insights and tools. (shrink)