In spite of the seeming heterogeneity of topics in its title - Revolutions, Systems, and Theories - this volume purports to be something more than a random collection of Essays in Political Philosophy. The Colloquium of the Philosophy Department of the University of Western Ontario (29-31 Octo- ber, 1971) at which initial versions of the first eight papers were delivered was entitled 'Political Theory'; and while the organizers anticipated and indeed welcomed topicality in the issues accorded priority arid in the empirical evidence invoked, they were also hoping for a reasonably comprehensive explorat ion of some of the central issues of political philosophy. For this reason it was quickly decided that in such a field a philosophical focus on clarification of ordering concepts required the suppIement - and test - of researches into more particular subject maUers by social scientists. Thus, to speak in general terms (where the specializatlons and their taxonomies multi- ply fissiparously!) , contributors include political scientists, economists and sociologists (Barnard, Baston, Tullock, Rapoport) as well as philosophers (Scriven, Morgenbesser, Braybrooke, TayIor), and juxtaposed as proponents and commentators *to generate exchanges across disciplinary frontiers. While the five additional invited papers are alI by professional philosophers, they extend the original Colloquium either by continuing controversy on its funda- mental issues (e. g. , Rubinoff, Nielsen, Roy) or by their continued explorations in what are acknowledged to be boundary areas (e. g. , Schick, Wartofsky). The greatest topical emphasis is that on revolution.