MAPPING AS THINKING: GEOLOGY AS THE PREMIER SCIENCE OF SYNTHETIC REASONING

Geology has been criticized by geochemist Claude Allegre (1988, The Behavior of the Earth) for its ‘mapping mentality’ pursued more as religion than as science with its disciples focused on ever finer scales while failing to generate important new concepts. How can the spatial cataloging of Earth’s messy details, “mere accumulation of facts,” be squared with the hypothetico-deductive method that is commonly presumed for all philosophy of science? Rather than exemplifying defects in scientific reasoning, however, I argue that geological mapping provides a premier exemplar for what sets geology apart in a most positive way from other physical sciences, and provides insight into why this is exactly the kind of science that is most needed in today’s uncertain world. As shown by David Oldroyd, “geomaps” first began to appear in the Renaissance, but it was not until the mid-18^th century that pictorial/spatial depictions of rocks and economically important materials were superseded by multi-color diagrammatic representations of Earth. The 4-dimensional character of true “geological” maps arose in the early 19^th century, when Smith, Cuvier, Brongniart, and others brought in the “actualized time” element through biostratigraphy. The logic of geological maps is most often characterized as both analytical and synthetic, and the most detailed study of these modes of inference is that of David Varnes (1974, The Logic of Geological Maps, U.S. Geol. Survey Prof. Paper 837). However, these conventional elements of explanatory philosophy have also generated misunderstanding of the creative, discovery-oriented role of abduction (retroduction) in the synthetic reasoning that is intrinsic to geological mapping. This mode of inference places the field geologist “in communication with Earth” in such a way that the interpretive character of geological mapping transcends the logical limitations of what scientists try to tell about Earth by letting Earth itself do the telling.