A survey of the Journal of the O.R. Society in 1978 shows that Ackoff's papers were part of a quite widespread and often pessimistic debate about the practical success of O.R. A similar survey for 1968 shows, on the other hand, a widespread mood of optimism. It is suggested that O.R. is now in a period of crisis analogous to that described by Kuhn in the Natural Sciences, when the dominant framework of assumptions appears to fail in relation to important problems. When such failures persist, alternative frameworks are proposed challenging the hitherto accepted view, and an increasingly wide-ranging debate develops. Many of the features of such debates, as outlined by Kuhn, seem to be present in the current controversy within O.R. More specifically, it seems possible in O.R. and related fields to identify three rival sets of proposals, which may be labelled official, reformist (e.g. Ackoffian) and revolutionary. However, the debate in O.R. differs from that in the Natural Sciences because it is not just about the best means of understanding the empirical world. It is also about the type of social world to be constructed through the framework of assumptions adopted. Our view is that in the current debate, proponents of the reformist stance will probably win. However, this may be very much an interim solution.