Abstract. This article considers the philosophical and experiential foundations of human perception of geographical phenomena and their abstraction and coding in geographical information systems. It examines the role of culture and language in describing geographical reality and explores the ways geographical data models reflect how people view the world. Differences between those who see the world as made of exact entities and smooth continuous surfaces, and those who prefer to view reality as a dynamic and complex are explored in terms of five aspects of spatial data, namely (i) objects versus fields, (ii) single scale versus multiple scales, (iii) Boolean versus multivalued logic, (iv) static versus dynamic descriptions and (v) determinism versus uncertainty. These five aspects are further divided into nine factors of geographical data which indicate the differences in the way people perceive spatial data. Eight “typical” GIS applications and four generic methods of handling spatial data are examined in terms of these nine factors to define a GIS “hyperspace”. The locations of the typical applications and the generic methods in this hyperspace show why no single generic approach to spatial data handling is sufficient for all possible applications. The analysis reinforces the authors' contention that spatial data analysis tools need to be chosen and developed to match the way users perceive their domains: these tools should not impose alien thought modes on users just because they are impressively “high tech”. The implications of this conclusion for choosing or developing spatial information systems, for data standardization and generalisation and for the further development of “GIS” as a discipline in its own right are presented as topics for further discussion.