100 YEARS OF NUMBERS - AN HISTORICAL INTRODUCTION TO MEASUREMENT THEORY 1887-1990 .1. THE FORMATION PERIOD - 2 LINES OF RESEARCH - AXIOMATICS AND REAL MORPHISMS, SCALES AND INVARIANCE

The aim of this paper is to reconstruct the historical evolution of th e so-called Measurement Theory (MT). MT has two clearly different peri ods, the formation period and the mature theory, whose borderline coin cides with the publication in 1951 of Suppes' foundational work, 'A se t of independent axioms for extensive quantities'. In this paper two p revious research traditions on the foundations of measurement, develop ed during the formation period, come together in the appropriate way, These traditions correspond, on the one hand, to Helmholtz's, Campbell 's and Holders studies on axiomatics and real morphisms and, on the ot her, to the work undertaken by Stevens and his school on scale types a nd transformations. These two lines of research are complementary in t he sense that neither of them is enough taken alone, but together they contain all that is necessary to develop the theory, and it is in Sup pes (1951) that these complementary approaches converge and all the el ements of the theory are appropriately integrated for the first time. With Suppes' work, then, begins what may be called the 'mature' theory , which was to develop rapidly later on, especially during the 1960s. Our historical reconstruction is divided into two parts, each part dev oted to one of the periods mentioned. Part I also contains a conceptua l introduction which aims to establish the use of some notions, specif ically those of measurement nr and metrization. Although the reconstru ction is not exhaustive, it intends to be quite complete and up to dat e compared to what is available in measurement literature; in this sen se the aim of this paper is mainly historical but, although secondaril y, it also attempts to make some conceptual and metascientific clarifi cations on the subject of the theory. Copyright (C) 1997 Elsevier Scie nce Ltd.