Darwinism defined: the difference between fact and theory - essay

We learn in high school about the scientific method -- a cut- and-dried procedure of simplification to essential components, experiment in the controlled situation of a laboratory, prediction and replication. But the sciences of history -- not just evolution but a suite of fundamental disciplines ranging from geology, to cosmology, to linguistics -- can't operate by this stereotype. We are charged with explaining events of extraordinary complexity that occur but once in all their details. We try to understand the past, but don't pretend to predict the future. We can't see past processes directly, but learn to infer their operation from preserved results.

Science is a pluralistic enterprise with a rich panoply of methods appropriate for different kinds of problems. Past events of long duration don't lie outside the realm of science because we cannot make them happen in a month within our laboratory. Direct vision isn't the only, or even the usual, method of inference in science. We don't see electrons, or quarks, or chemical bonds, any more than we see small dinosaurs evolve into birds, or India crash into Asia to raise the Himalayas.

William Whewell, the great English philosopher of science duringthe early nineteenth century, argued that historical science can reach conclusions, as well confirmed as any derived from experiment and replication in laboratories, by a method he called ''consilience'' (literally ''jumping together'') of inductions. Since we can't see the past directly or manipulate its events, we must use the different tactic of meeting history's richness head on. We must gather its won- drously varied results and search for a coordinating cause that can make sense of disparate data otherwise isolated and uncoordinated. We must see if a set of results so diverse that no one had ever considered their potential coordination might jump together as the varied products of a single process. Thus plate tectonics can explain magnetic stripes on the sea floor, the rise and later erosion of the Appalachians, the earthquakes of Lisbon and San Francisco, the eruption of Mount St. Helens, the presence of large flightless ground birds only on continents once united as Gondwanaland, and the discovery of fossil coal in Antarctica.

Darwin, who understood the different rigor of historical scienceso well, complained bitterly about those critics who denied scientific status to evolution because they couldn't see it directly or reproduce its historical results in a laboratory. He wrote to Hooker in 1861: ''Change of species cannot be directly proved . . . The doctrine must sink or swim according as it groups and explains phenomena. It is really curious how few judge it in this way, which is clearly the right way.'' And later, in 1868: ''This hypothesis may be tested . . . by trying whether it explains several large and independent classes of facts; such as the geological succession of organic beings, their distribution in past and present times, and their mutual affinities and homologies.''