 So far I have noted that an operational definition is not sufficient to express a concept’s meaning fully. Going further than that, many critics of operationalism have argued that not every good scientific concept needs to have an operational definition. If operationalism means demanding that every concept and every inferential step should have an immediate operational significance, it constitutes an overly restrictive empiricism. At times Bridgman did appear to be making such a demand, as illustrated in the poignant episode (discussed in Section 1.3 above) in which he criticized Einstein for betraying his own operationalist lesson in the general theory of relativity. Einstein’s view was that there was no reason for physicists to shrink from using a non-operational concept if that delivered good results.