Analogy is widely considered to be an important mechanism of scientific thinking and a source of creative insight in theory development (e.g., Tweney, Chapter 13, this volume). No less an authority than Johannes Kepler stated: “And I cherish more than anything the Analogies, my most trustworthy masters. They know all the secrets of Nature, and they ought to be least neglected in Geometry” (quoted in Polya, 1954, p. 12). In addition to its uses in scientific discovery, analogy functions as part of the workaday tool kit of science. In instruction, novices are told to think of electricity as analogous to water or of addition as analogous to piling up blocks, and in problemsolving analogy is a standard tool among both experts and novices (e.g., see Clement, 1981; Collins & Gentner, 1987; Gentner & Gentner, 1983; Van Lehn & Brown, 1980). Finally analogy is also used in everyday reasoning, as when the stock market is said to “climb to dizzying heights” or when there is said to be a “balance of trade” (see Lakoff & Johnson, 1980).

Yet for all its usefulness, analogy is never formally taught to us. We seem to think of analogy as a natural human skill, and of the practice of analogy in science as a straightforward extension of its use in common-sense reasoning. For example, William James believed that “men, taken historically, reason by analogy long before they have learned to reason by abstract characters” (James, 1890, II, 363).