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.