His research interests include metaphysics and ontology, the history of logic, the history of Central European Philosophy, particularly in Austria and Poland in the 19th and 20th centuries, and the application of metaphysics to engineering and other non-philosophical disciplines. He is the author of two books and over 200 articles. He is currently working on a project supported by the British Academy to chart the metaphysics of quantity.
Parts. A Study In Ontology, Oxford: Clarendon Press, 1987.
Philosophy and Logic in Central Europe from Bolzano to Tarski. Selected Essays, Dordrecht: Kluwer, 1992.