In the philosophy of
The length of a rod, for example, may be defined as the number of times a certain stick can be laid end to end alongside it. Propositions that are not amenable to verification through measurement and observation are rejected as meaningless (See also {{link=logical positivism">logical positivism ). Operationalists rejected the idea of nature as a thing-in-itself existing behind the appearances observed in experimentation. Operationalism is closely associated with the work of the U.S. physicist Percy W. Bridgman (1882–1961).