This chapter addresses two areas in which the interests of political scientists overlap with those of philosophers of science: how political science should be understood as a science and causal inference. The examination of the history of political science reveals that these are closely connected. During the twentieth century political scientists often strove to make the discipline “more scientific”, evoking what Karl Popper called “the demarcation problem”. One prominent answer to that question was that science required establishing causal relations among the phenomena. This, in turn, led to methodological debates about how to produce the best evidence for causal inference, since different methods would seem to produce different sorts of evidence. The chapter explores how current philosophical discussions about evidence for causal claims have intersected with those methodological debates, looking particularly at multi-method research and evidential pluralism.