 In closing, I would like to pull out an insight from Bridgman that is usually not recognized in discussions of operationalism, but actually has emerged as a significant point of contention in more recent philosophy of science. This is the issue of complexity. In Section 1.1 I have already quoted Bridgman’s puzzling statement that nature is ultimately “neither understandable nor subject to law.” As it turns out, that was not an isolated off-hand remark. An important aspect of Bridgman’s operationalism was a search for certainty, and it was a search made all the more desperate by a deep-rooted pessimism about the possibility of attaining any certainty in science, at least if scientists were to seek a simple and unified system of knowledge. Bridgman professed his belief that “the external world of objects and happenings is … so complex that all aspects of it can never be reproduced by any verbal structure.” He lamented: “Even in physics this is not sufficiently appreciated, as is shown, for example, by the reification of energy. The totality of situations covered by various aspects of the energy concept is too complex to be reproduced by any simple verbal device.” (Bridgman in Frank 1956, 78)