This article reconsiders the role of mechanisms in social science research. The study of mechanisms has been recognized as a fundamental task for a methodologically diverse range of social scientific approaches. This raises questions of what roles mechanisms play for causal explanations and if there are uses that are more reasonable than others. To address these questions the article, first, discusses competing arguments for the causal theory underpinning mechanisms. On the basis of these discussions the paper emphasizes the heuristic role of mechanisms as an explanatory devise, serving a crucial role for causal explanations. Secondly, it endeavors to explore the diverse ways mechanisms are employed, especially in contemporary political science research, to highlight limits and benefits with different approaches. The discussion helps reconsider existing fault lines in debates over mechanisms, including the relationship between qualitative and quantitative techniques in empirical research centered on mechanistic explanations.