 Bridgman’s position on the matter of theoretical concepts was complicated, and perhaps not entirely self-consistent (I will return to this point in Section 3.3). One common objection to operationalism is based on a misunderstanding that reveals an essential difference between Bridgman and most of his critics. It is often said that operationalism cannot be right because each scientific concept can be measured in various ways. This criticism is based on the presumption that the concept in question has unity, which means that its definition must also be unified. If there are a variety of measurement methods all of which apply to one concept, then measurement methods cannot be what supplies the unified definition; instead, some theoretical account must be given as to how the variety of operations under consideration serve to measure the same thing. Bridgman, in contrast, had no such presumption of conceptual unity. For him, the initial position to take was that if there are different methods of measurement we have different concepts, as he said about “tactual” and “optical” length being two different concepts. Now, it could be that there is one aspect of reality that different measurement operations all get at, but that is something to be demonstrated, not to be assumed at the outset. The possibility of unity can be entertained if the minimum condition of numerical convergence is met—that is, if two measurement operations have an overlapping range and their results agree in the overlap. Still, Bridgman maintained some skepticism about whether it was safe for us to infer real conceptual unity from such numerical convergence.