This article explores a central concept of classical economics (equilibrium) from an experiential cognitive science point of view, assuming that model-building in science is an analogy-like manifestation of metaphoric thought. In order to account for the metaphorical basis of the concept, it studies the argumentation of various economists, including the authors of an economics textbook for first year students, and comes to the conclusion that there is an obvious reason why this and many other concepts of classical economics are based on Newtonian physics analogies, viz. that such analogies originate in our primary bodily experience. The article winds up with a discussion of indeterminacy in the languages of classical and modern economics.