This is the editorial for a festschrift for Mike Jackson. We begin by outlining six phases of Jackson's research, from 1982 to the present day: an initial critique of soft systems thinking and soft operational research (OR); a proposal for methodological pluralism to overcome the hard/soft divide; a description of an ‘enhanced systems/OR’ that acknowledges the complexities, uncertainties and conflicts regularly encountered in practice; the further development and popularization of his enhanced OR under the banners of ‘critical systems thinking’ and ‘total systems intervention’; the consolidation of his work in three books with mature presentations of his perspective; and a rethinking of the history of both systems thinking and systems science, accompanied by a renewed focus on the implications of his methodological ideas for systems practice. Following this outline, we move on to an overview of the papers in the festschrift, each of which either expands on Mike Jackson's ideas, applies them in new application domains, or critiques those ideas and provides alternatives.