ABSTRACT
Hans Vaihinger’s philosophy of “as if” introduced fi ctionalism into philosophical discussions in the early years of the 20th century.2 Vaihinger’s thesis was radical: A knowledge worth pursuing is thoroughly infused by fi ctional assumptions. Vaihinger distinguished carefully fi ctions from hypotheses, and considered most of science and mathematics to engage shamelessly in the production, dissemination, and application of both. Hypotheses are directly verifi able by experience and their truth is tentatively granted. Fictions are, for Vaihinger, accounts of the world and its systems that not only are plainly and openly false, but knowingly so, yet remain indispensable in theorizing-in science and elsewhere. However the fi ctions employed in scientifi c reasoning are not of the same kind as those that appear in other areas of human endeavor. Vaihinger distinguished scientifi c fi ctions from other kinds of fi ctions (such as poetic, mythical, or religious fi ctions), and he understood the difference to be one of function. Virtuous fi ctions play a role in a particular kind of practical rationality in scientifi c theorizing, a kind of “means-end” rationality at the theoretical level. In Vaihinger’s terminology, they are expedient.3 These are the fi ctions that fi gure in the scientifi c enterprise, and among the most prominent throughout the history of science Vaihinger identifi ed forces, electromagnetic “lines” of force, the atom, and the mathematical infi nity, as well as some of the main constructs of differential analysis such as infi nitesimal, point, line, surface, and space.
