ABSTRACT
This chapter examines a chronological approach and the role of constants in equations, comparing and contrasting the accounts of N. R. Campbell and B. D. Ellis, who have provided the most explicit and detailed descriptions of the role of constants in measurement. It reviews the principal traditional accounts of measurement in so far as they relate to constants. The chapter explains the aspects of the physical and mathematical systems in which constants are embedded without the confusion evident in the account of Campbell, nor the operationalist dogma of Ellis. In their accounts of measurement, both Campbell and Ellis explained how new quantities may arise in science from equations which involve quantities which have already been measured. At the heart of all measurement is a linkage between an empirical system of objects and relations, and a representational system of numerals and numerical relations.
