Contributor(s): Dr Bryan Roberts, Professor Mairi Sakellariadou | Galileo famously wrote that natural philosophy is “written in the language of mathematics”. Why is it that abstract pieces of mathematics, like an imaginary number, often later turn out to be surprisingly effective in describing concrete aspects of the natural world? Eleanor Knox is a Leverhulme Early Career Research Fellow in the Department of Philosophy at King’s College London. Mairi Sakellariadou is a professor of theoretical physics at King’s College London. Bryan Roberts is assistant professor in the Department of Philosophy, Logic and Scientific Method at LSE and Forum for European Philosophy fellow.