Synthetic biology is a research field that has grown rapidly and attracted considerable attention. Most prominently, it has been labelled the ‘engineering of biology’. While other attempts to label the field have been also pursued, the program of engineering can be considered the core of the field’s disciplinary program, of its identity. This article addresses the success of the ‘engineering program’ in synthetic biology and argues that its success can partly be explained by distinct practices of persuasion that aim at (...) persuading scientific, but also non-scientific audiences. The article explores two different modes of persuasion:, building tools as heuristic models and posing visionary claims. Objects such as the toggle switch or the synthetic oscillator in synthetic biology can more adequately be described as heuristic models of engineering instead of simply as prototypes of ‘tools’. Posing visionary claims can be also understood as a persuasion practice, since the claims are used to construct the societal relevance of the field. Drawing upon Michel Callon’s ‘sociology of translation’, I argue that both practices of persuasion aim at ‘enrolling’ entities into the disciplinary identity. The article is based on the textual analysis of rhetorical practices in three synthetic biology review articles which are considered seminal for the history of the field. (shrink)