You might consider this as Part 2 of the blog from December 9, 2018, Celebrating Helmholtz, in which I mentioned ordering a copy of Helmholtz’s Treatise on Physiological Optics, Volume III. After an odyssey obtaining it through a bookseller in England, I finally had the chance to digest its 700 plus pages. I have to admit that I found much of it to be ponderous and tangential, but that may be because it’s a multi-authored translation of his original work.
Why the obsession with Helmholtz, you’re wondering? Because his approach to visual development and binocular vision is at the center of controversy in the opening chapter of the book on binocular vision and ocular motility authored by von Noorden and Campos (an excellent resource available in its entirety online) which contains the following passage:
“Historically, there were two opposing schools of thought with regard to the origin and development of normal binocular vision and spatial orientation. One maintained that humans are born without binocularity or spatial orientation and that binocularity and spatial orientation are learned functions acquired by trial and error through experience and assisted by all the other senses, especially the kinesthetic sense. This is the theory of empiricism: that binocular vision depends on ontogenetic development. The other school held that binocular vision and spatial orientation are not learned functions but are given to humans with the anatomico-physiologic organization of his visual system, which is innate. This is the nativistic teaching: that binocular vision is acquired phylogenetically rather than ontogenetically.”
A close look at the 3rd edition of Helmholtz’s Physiological Optics, in particular its appendix authored by Johannes von Kries (considered to be Helmholtz’s primary protégé) sheds more light on this important distinction of vision being an innate process (as espoused more by Hering) as opposed to a learned process (as espoused by more Helmholtz). von Kries writes (pages 623-624):
“First of all, there cannot be any doubt as to the fact that both innate substructures and a process of development based on experience each contributes to establish the laws of localization as they are known to exist in the vision of adults … While it is possible that in these respects primitive or congenital dispositions contribute to a certain extent to the laws of localization, those space-determinations actually obtaining in developed vision are undoubtedly acquired, as shown by the fact that they are all relations with respect to the observer’s body, and cannot be separated from the idea of the body itself … A comprehensive way of expressing it would be to say that developed spatial vision is the results of a process of learning, for which however, certain preparations are made by innate dispositions, or which is initiated by them, as we might say. The learning itself must undoubtedly be regarded as a process of physiological development.”
von Kries concludes that it would be a mistake to think of nativism and empiricism as two mutually antagonistic conceptions involving a choice one way or the other. Experience is placed in the foreground in the empirical theory, and innately determined relations are in the foreground of nativistic theory, but whether a line should be drawn between the two and, if so, where to draw it, will always be a matter of personal opinion.