Toward the turn of the century, the study of sensation and observation as epistemological foundations for scientific knowledge gained increasingly significance. Famous natural scientists such as Helmholtz, Hering, Mach and Planck participated in debates about the nature of visual and auditory sensations and their processing and interpretation. Franz Boas, who was influenced and supported by Helmholtz, focused on visual sensations and observation in his doctoral dissertation. However, Boas was not satisfied with the prospect of psychophysics and could not settle with the trend in geography at the time in the United States, either.
This paper traces how approaches to auditory and visual sensations in controversies of physics stimulated and were simultaneously influenced by Neo-Kantian reflections on scientific knowledge, and further contributed to the developing distinction between Natur- and Geisteswissenschaften. I shall argue that Boas's empirical positivism has its roots in this Neo-Kantian debates on sensations in the philosophically informed natural sciences. Although his cultural relativism combining the plasticity of bodily types, the psychic unity of mankind, and diversity of cultures has to be understood in the same context, the deeper implications of this position was not the same as that of relativity in physics, which confirmed the universality and validity physics theory and methods. On the contrary, Boas's positivism led to a particularistic outlook, seemingly lacking theoretical or methodological coherence. It is his insistence on the analysis of secondary explanations about cultural phenomena which forms the key to a conversational model of culture, epistemology, and scientific knowledge.