 In the third part of Helmholtz’s Handbook of Physiological Optics, Helmholtz draws a distinction between nativism and empiricism in the physiology of perception. In drawing up the Handbook, Helmholtz’s “task was to survey the field of physiological optics for the purpose of writing a work that would appear as volume nine of Karsten’s Encyklopädie der Physik. The format of the Karsten series dictated that Helmholtz provide a thorough review of both past and present work, a task he performed diligently. Wishing to provide a systematic theoretical framework for his survey of the field, Helmholtz divided the major theoretical positions with respect to spatial perception into two groups, which he characterized with the adjectives empiristisch and nativistisch” (Hatfield 1991, 274–275. I follow Hatfield in translating the term “empirismus” as “empirism.”). Turner (1993) has argued that Helmholtz’s empirism was pragmatic – that Helmholtz adopted an empirist stance to meet the challenges of “imposing order on a chaotic new field of investigation” and of defending his stance in his lifelong debate with Ewald Hering (Turner 1993,155). 