Duncan's research and teaching stand at the intersection of political theory, intellectual history, and International Relations. Over the last couple of decades he has focused principally on tracing ideas about empire – and in particular settler colonialism – in the history of modern British political thought. He has written three books on the subject, as well as assorted articles and book chapters. He has also worked on various topics in contemporary political theory and IR.  

His current research explores how the future of humanity has been imagined – by philosophers, scientists, and fiction writers – in Britain and the United States since the late nineteenth century. 

Duncan is Co-Director of the Cambridge Centre for Political Thought and Co-Convener the POLIS History and IR programme. He has held visiting positions at Columbia, Harvard, Darmstadt and the FU Berlin. 

In 2012 he was awarded the Philip Leverhulme Prize for his work on the history of political thought.

In 2021 he was elected a Fellow of the British Academy.

At Christ's, Duncan is Part II Director of Studies for Politics and Sociology.