Realism, functions, and the a priori: Ernst Cassirer's philosophy of science

•Presents the main ideas of Cassirer's general philosophy of science.•Shows how these main ideas follow from his contrast between substance and function.•Gives a reading of Cassirer's conception of realism and the a priori.•Argues against some recent interpretations and well-known critics.•Explains why Cassirer rejects conventionalist philosophies of science.

This paper presents the main ideas of Cassirer's general philosophy of science, focusing on the two aspects of his thought that—in addition to being the most central ideas in his philosophy of science—have received the most attention from contemporary philosophers of science: his theory of the a priori aspects of physical theory, and his relation to scientific realism.