Abstract

Of S. S. Stevens's well-known classification of nominal, ordinal, interval and ratio ‘scales of measurement’, perhaps its least-known aspect is its most distinctive, namely the distinction between interval and ratio scales. This article investigates the circumstances of the typology's origins among the experimental psychologists at Harvard in the 1930s and the unique fusion of personal, technical and intellectual forces this setting represented. It shows how it came to be that an influential psychologist reconceptualized measurement from first principles in such a way as to both preserve the distinction between psychology and physics in this regard and yet implicitly classify his own work as the latter. The article concludes with the general suggestion that, if it is necessary to measure something, it might as well be something tangible enough to be measured usefully