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Soil ScienceSociety of America Journal 61:523–33.746 MalansonCorrespondence: Dept. of Geography, University of Southern California, email [email protected] (Wilson);Utrecht Centre for Environment and Landscape Dynamics, University of Utrecht, Postbus 80.115, 3508 TCUtrecht, The Netherlands (Burrough).Like an ember in a lightning-struck bolethat may flare up in a dry wind, an episte-mological conflict has smoldered in physi-cal geography since the rise of general systemstheory. This conflict, often unrecognized andimplicit, is over the relative merits of reduction-ism and holism (cf. Allen and Starr 1982;Phillips 1999). Reductionism seeks explanationthrough the isolation of parts of a phenomenoninto the smallest units and the examination ofinteractions between pairs of these parts. Thephenomenon is explained as the sum of the partsand their pairwise interactions. Holism ad-dresses the behavior of a whole structure, seek-ing explanation in the identification of thesimplest explanatory principles. Both ap-proaches have strengths and weaknesses.Reductionism discriminates well among expla-nations using data, yet does not necessarily findthe simplest principles; moreover, it does nothave a philosophical basis for selecting phenom-ena to study. Holism finds the simplest explana-tions if sufficient data exist for studying theinteractions of a phenomenon. Where such dataare lacking, however, holism does not easily dis-tinguish among alternative hypotheses. While agradient exists between the two approaches,their difference is significant because theextremes lead to fundamentally different ques-tions and to different answers to the same ques-tions. In physical geography, although notnecessary to the conflict, general systems theoryprovides a rationale for both reductionism, as away to avoid unimportant questions, andholism, as a link to basic processes.A second, rarely mentioned methodologicalconflict exists in physical geography: the rela-tive merits of empiricism and theory. While, inmany sciences, the two are seen as complemen-tary but competitive—and practiced separatelyConsidering ComplexityGeorge P. MalansonDepartment of Geography, University of Iowa(experimentalists deride theorists, and viceversa, in physics and biology)—little spaceexists in physical geography for theorists. As faras I know, all physical geographers engage inempirical work, so much so that theorists inrelated fields expect geographers to be empiri-cists. Attempts to construct and analyze simpletheoretical models in physical geography arerare.Ecology addresses the conflict betweenholism and reductionism openly (e.g., Weigert1988; Inchausti 1994; Weber and Schmid 1995;Bergandi and Blandin 1998; May 1998), and somay help inform physical geography throughbiogeography. The debate in ecology arisesbecause ecological systems, like those in physicalgeography, are middle-number systems: ones inwhich there are too many parts to representindividually and too few to capture statistically.In ecology, the conflict is recognized as an issueof spatial and temporal scale—and scale is nowa fundamental concern of ecologists. The con-flict has been conceptualized under the rubric ofhierarchy theory, which posits that observationscan be divided into levels, within which one canlocate the observer (e.g., Allen and Starr 1982;Pahl-Wostl 1993; Ahl and Allen 1996). Lowerlevels help identify processes that build structureat middle levels, which are in turn constrainedby structures at yet higher levels.In their identification of methodologicalissues in physical geography, Bauer et al. (1999)are fundamentally concerned with scale. Theycharacterize a strong trend toward reductionismin physical geography over the past threedecades, as demonstrated in studies of steady-state conditions using algebraic or differentiallinear equations. They argue for longer time-span studies, incorporating cyclic processesusing differential and partial differential non-linear equations. Although physical geography isconcerned with phenomena with many interact-ing parts, we tend to simplify our research ques-tions to conform to mathematically tractabledomains of one scale; as a result, our methodol-ogy is constrained by our techniques. The limi-tations that simplification toward tractablemathematics have placed on us are not, how-ever, based only in mathematics. The domina-tion of a systems approach in physical geographyhas led, perhaps surprisingly, to increasing faithin reductionism (Strahler 1992). Instead of ageneral picture of landscape processes based ona system, we increasingly investigate the pair-wise relations within a system. On the otherhand, even when a larger structure is the object,we are constrained in our