Nature - autonomous learning

214 the dis/unity of geographybank-form, for instance, could alter the operation of processes (like turbulence)governed by general laws of mechanics (see Lane and Roy 2003).In sum, physical geographers are currently debating whether theirs isultimately a nomothetic field science (concerned with general processesunderpinning various patterns and forms) or ultimately an idiographicfield science (concerned with unique patterns and forms underpinnedby equally unique conjunctions of general processes with specific localconditions).Epistemological issuesAll ontological beliefs depend, in part, upon epistemological ones.Whatwe believe to be real is influenced by how we think we can come to knowreality. Here I identify three important epistemological issues that physicalgeographers have wrestled with in recent times.The first is the questionof whether or not ‘seeing is believing’ (what’s usually called empiricism).Increasingly, physical geographers argue that there is more to reality thanmeets the eye.Though physical geography is heavily empirical this doesnot mean it is necessarily empiricist. Fluvial geomorphologists influencedby the philosophy of transcendental (or critical) realism have made thisargument very forcefully (see Richards 1990). Transcendental realistsargue that we need a ‘depth ontology’ if we’re to understand reality properly.A flat, empiricist ontology implies that reality consists only of what isobservable (and is an ontology characteristic of positivism). A depthontology, by contrast, makes a distinction between structures, mechanismsand events. Structures are invisible but real elements of reality (like gravityor energy conservation) that undergird the behaviour of many phenomena.In turn, these structures operate on animate and inanimate matter andare expressed as mechanisms (like water turbulence or air convection).Finally, these mechanisms give rise to visible effects (events) of the kindthat physical geographers study. For transcendental realists this depthontology undermines empiricism and ensures that the researcher playsan active role in identifying what is real as opposed to merely observable.For instance, a fluvial geomorphologist studying a pool-and-riffle sequencemay surmise that multiple structures and mechanisms intersect to create thephenomena observed (see Figure 4.7).What is more, this conjunction ofcausal processes may be influenced by so-called ‘contingent conditions’(like the morphology of the river bed and profile) such that the same