Philosophy in physical geography is done as much by boots and compass as by mental activity. Philosophy in physical geography is an active process open to change as the subject is practiced. This book taps into philosophy in action in physical geography by exploring the links between the two and their relations to scientifi c thought as a whole. Recent developments in geography have highlighted the need for a source of information on the philosophical basis of geography. Texts on the philosophical content of human geography are relatively common (Gregory, 1978; Kobayashi and Mackenzie, 1989; Cloke et al. , 1992). Texts that serve the same purpose for physical geography are thinner on the ground. Apart from the classic Haines-Young and Petch (1986) text on physical geography, there is little accessible to undergraduates that discusses how physical geographers think about and use philosophy within their work. Some physical geographers may regard this as a good thing, automatically stating the Chorley (1978) quote about reaching for their soil auger when they hear the term philosophy (although the rest of the text beyond this infamous quotation is in favour of a more thoughtful approach to the subject). Physical geography has been and still is about ‘doing’ rather than theorising in the passive sense of ‘armchair’ geography, an attitude with which many physical geographers interpret the term. This book is not intending to dispute the active and refl ective nature of physical geography, in fact this book is only possible because physical geography is a subject that views itself as fi rst and foremost about practice. The activities of physical geographers, the practice of their subject, involves a vast array of philosophical decisions, even if most are implicit or seen as part of the tradition or training associated with a particular fi eld. Importantly, physical geographers, as all good scientists, question what they are looking at – they do not necessarily take the world for granted as it is. They defi ne, they classify, they probe, they question and they analyse. Why is this not seen as philosophical?