 Recognizing the importance of empirical content helps us make sense of Bridgman’s complex attitude toward theoretical concepts. In a little-known section of The Logic of Modern Physics, he discussed what he called “mental constructs” in science, particularly those created in order to “enable us to deal with physical situations which we cannot directly experience through our senses, but with which we have contact indirectly and by inference” (1927, 53–60). Not all constructs are the same: