The Euclidean model of measurement in Fechner's psychophysics.

Historians acknowledge Euclid and Fechner, respectively, as the founders of classical geometry and classical psychophysics. At all times, their ideas have been reference points and have shared the same destiny of being criticized, corrected, and even radically rejected, in their theoretical and methodological aspects and in their epistemological value. According to a model of measurement of magnitudes which goes back to Euclid, Fechner (1860) developed a theory for psychical magnitudes that opened a lively debate among numerous scholars. Fechner's attempt to apply the model proposed by Euclid to subjective sensation magnitudes--and the debate that followed--generated ideas and concepts that were destined to have rich developments in the psychological and (more generally) scientific field of the twentieth century and that still animate current psychophysics.