ABSTRACT
This chapter describes how G. T. Fechner’s knowledge of ideas about measurement and about variability was initially grounded on measurements of physical intensity. It discusses Wilhelm Whewell’s contributions to the study of measurement. Moving to the measurement of the intensity of light, Whewell considered as “inadmissible” all so-called photometers that appeared to measure light intensity in terms of the amount of heat that produced that light. Whewell discussed only the measurement of intensive magnitudes applied to physical entities. Whewell’s historical account of the difficulties associated with the measurement of physical sound intensities, physical light intensities, and physical heat intensities, was summarized. Whewell’s mid-nineteenth-century achievements were far-sighted anticipations of twentieth-century theories of measurement of sound, light, and heat. Whewell’s treatment of the difference between intensive and extensive measurement-units seems exemplary for its time. In approaching psychophysics, the magnitudes of particular interest to us are clearly specifiable stimulus intensities and, more controversially, sensation-magnitudes.
