Opinion appears sharply divided on the value of studies which attempt to forecast the future. On the one hand we have those such as Ackoff (1981 :ix) who argue that To the extent that we can control the future we do not have to forecast it… To the extent that we can respond rapidly and effectively to changes that we neither control nor expect… we need not forecast them’. Others (e.g. May 1982) argue for more future-oriented planning where the typical objective is to generate a number of probable scenarios in order to understand the implications of future movements for the present (i.e. to identify those policy and planning decisions required now in order to avoid or achieve possible future conditions). Yet in so far as the future is open to change by human planning, can it be open to forecasting (see Vickers 1981)?. If we follow the logic of Bell and Mau (1971) then the answer is probably yes, so long as the model of the future is probabilistic rather than purely deterministic because, until the future has become the present, some alternative possibilities remain open.