 Length, for example, would be defined as the result of the operation of concatenating rigid rods. According to this extreme version of operationalism, different operations measure different quantities. Length measured by using rulers and by timing electromagnetic pulses should, strictly speaking, be distinguished into two distinct quantity-concepts labeled “length-1” and “length-2” respectively. This conclusion led Bridgman to claim that currently accepted quantity concepts have “joints” where different operations overlap in their domain of application. He warned against dogmatic faith in the unity of quantity concepts across these “joints”, urging instead that unity be checked against experiments whenever the application of a quantity-concept is to be extended into a new domain. Nevertheless, Bridgman conceded that as long as the results of different operations agree within experimental error it is pragmatically justified to label the corresponding quantities with the same name (1927:  16).[8]