The introduction establishes the theoretical grounds for the analysis of mathematics and modernism and situates the book within the critical contexts of modernism and science studies and literature and science studies. It sets out the unique epistemological status of mathematics, key stages in its historical development, and charts the new territory that the book opens up by examining literary engagements with mathematics and modernism. With reference to texts and theories by Herbert Mehrtens, Jeremy Gray, Leo Corry and Moritz Epple, the introduction establishes the concept of modernist mathematics, the role of the so-called ‘foundational crisis of mathematics’, and competing logicist, formalist and intuitionist positions, particularly as represented by David Hilbert and L.E.J. Brower. The introduction also sets out how the issues at stake in mathematics feed into the modernist revaluation of rationality and Enlightenment values and echo the sense of crisis in other areas. A particular focus is on theories that reflect on mathematics as a human construct and deliberately created fiction, including texts by Friedrich Nietzsche, Ernst Cassirer, Oswald Spengler, Hans Vaihinger, Hartry Field and Alain Badiou.