 Molecular biologists discover and explain by identifying and elucidating mechanisms, such as DNA replication, protein synthesis, and the myriad mechanisms of gene expression. The phrase “theory of molecular biology” was not used above and for good reason; general knowledge in the field is represented by diagrams of mechanisms (Machamer, Darden, and Craver 2000; Darden 2006a, 2006b; Craver and Darden 2013; Baetu 2017). Discovering the mechanism that produces a phenomenon is an important accomplishment for several reasons. First, knowledge of a mechanism shows how something works: elucidated mechanisms provide understanding. Second, knowing how a mechanism works allows predictions to be made based upon the regularity in mechanisms. For example, knowing how the mechanism of DNA base pairing works in one species allows one to make predictions about how it works in other species, even if conditions or inputs are changed. Third, knowledge of mechanisms potentially allows one to intervene to change what the mechanism produces, to manipulate its parts to construct experimental tools, or to repair a broken, diseased mechanism. In short, knowledge of elucidated mechanisms provides understanding, prediction, and control. Given the general importance of mechanisms and the fact that mechanisms play such a central role in the field of molecular biology, it is not surprising that philosophers of biology pioneered analyzing the concept of mechanism (see the entry on mechanisms in science).