A political theorist and historian of political thought, Ryan is a recognised authority on development of modern liberalism, and especially the work of John Stuart Mill, having contributed directly to the 'Reversionary' school, which led to a re-examination of Mill's work from the 1970s.
Ryan is a regular contributor to The New York Review of Books, the London Review of Books, and The Times Literary Supplement, and continues to write on political theory and the history of political thought [REF].