The Concept of Mass

In the analytic-empirical philosophy of science, technical terms not explicitly defined are referred to, within a two level model of scientific language, as “theoretical concepts” or “theoretical terms”. After it had proved impossible to reduce physical terminology to a non-theoretical observational language by means of explicit definitions or complete interpretations of all the terms of a theory, the term “theoretical concept” in the work of C. G. Hempel was first interpreted to mean that such terms cannot be defined or determined explicitly and independently of the complex of the other terms in a particular theory. Nor can they be defined independently of the empirical validity or corroboration of this theory.1