I have broad philosophical interests, though most of my research falls into two main areas: (i) philosophy of biology / evolutionary theory; and (ii) epistemology /philosophy of science.

Within philosophy of biology, I am especially intereted in foundational and conceptual questions surrounding evolutionary theory. For many years, my research focused on the 'levels of selection' question in evolutionary biology, and the related issue of individual versus group conflicts of interest. This culminated in my book Evolution and the Levels of Selection (OUP 2006), which was awarded the 2009 Lakatos Prize for an outstanding contribution to philosophy of science. I continue to work on these topics.

From 2008 to 2011 I was Principal Investigator on a major AHRC-funded research project, 'Evolution, Cooperation and Rationality', in collaboration with Professor Ken Binmore, which led to a series of publications and an edited volume Evolution and Rationality (CUP 2012).

From 2011 to 2016 I was Principal Investigator on a research project entitled 'Darwinism and the Theory of Rational Choice', funded by a European Research Council Advanced Investigator Award. The aim of the project was to study connections, formal and conceptual, between Darwinian evolutionary theory and the theory of rationality. This culminated in a book, Agents and Goals in Evolution, published by OUP in 2018.

Within epistemology / philosophy of science, I am interested in topics including probability and induction, evidence and confirmation, causality, theory choice, scepticism and knowledge, and epistemological holism. I continue to work on these topics when time permits.