Empedocles' theory of vision

Date

1986

Authors

Caston, Victor, 1963-

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For most people, Empedocles' comments on vision represent a curiosity at best, where scholars' attempts to render them less subject to ridicule have often only made them more so. Even when sympathetic, such renderings have in general been apologetic, and thus tacitly concede the substance of his detractors claims. More often, Empedocles has been suspected of practicing a speculative and a prioristic "science". A reasonably straightforward reading of the texts, however, will show that Empedocles' method was scientific, and in the best sense of the word: his conclusions were based on detailed observations of the structures involved in vision and an attempt to explain their functions in terms of his own physical theories. In particular, he was concerned with the macroscopic, external features of the eye (such as iris and pupil) and puzzling yet familiar phenomena associated with vision (most especially night vision and the changing appearances of animals' eyes). By correlating these features with the elements of his theory, he was able to explain their interactions according to the more general principles of his physics. In short, what Empedocles attempted was nothing less than a physiological account of vision. After extensive detailing of what was available to unaided observation, Empedocles did finally embark on speculative notions, a brief excursion, limited solely to the mechanism of the semi-permeable membrane which contains the eye. Yet even here, his theory is grounded in and enhanced by the observation of available models, namely, the linen screens of lanterns and the conjunction of biological orifices and their counterparts. Having pushed his observations to their natural limits, he did appeal to analogy, but only to postulate the existence of a mechanism which operated on otherwise familiar principles. In this regard, Empedocles was no more frivolous than any other creative scientific mind. All of these conclusions follow from an attentive reading of the testimonia. Most of the difficulties in interpreting Empedocles' theory have, in fact, been problems engendered by commentators themselves; the most salient example is the comparison with the theory of vision in Plato's Timaeus, a parallel first drawn by Aristotle and predominant in the literature ever since. Interpretations have often been misled by parallels and concerns external to Empedocles' own work and not properly examined. In light of this, any interpretation which lays claim to being a coherent and harmonious account of Empedocles' theory must not only compass all the doctrines relevant to his theory, but survey the grounds of past misunderstanding as well, just as it must find its fundament solely in the texts as extant, while also suggesting the greater dimensions of Empedocles' philosophy as a whole. A more direct approach to the testimonia will easily yield such an interpretation, but a patient and arduous critique of the commentators will be necessary, if the overgrowth which they have cultivated is at last to be cleared away. In the present paper, the summary of Empedocles' theory in Theophrastus' De Sensibus will serve as the primary basis for interpretation. Not only is Theophrastus' report detailed and comprehensive, but it is also exceptionally clear, and therefore offers the least possibility of misunderstanding. Moreover, his summary lacks the eristic arguments which so often mar Aristotle's comments and even make his own criticisms of Empedocles difficult to evaluate. Using his summary as a guide, then, the first section of this paper will establish the basic framework of Empedocles' doctrines: the global features of the eye, their functions and their interactions. In the second section, the nature and function of the membranes will be more precisely determined in an attempt to specify the exact mechanism through which vision as a whole is effected. This analysis can only be acheived through the exegesis of the more difficult testimonia of Aristotle (most especially the lantern fragment, DK 31 B 84) and Theophrastus' critique of Empedocles' in the De Sensibus. Only on the basis of this critical foundation will it be possible finally to attempt to comprehend Empedocles' thoughts on vision as a whole and to reveal his philosophical insights on the nature of perception. Empedocles stands on the brink of Greek science: though his language is still cloaked in the figurative style of poetry, his method is physiological

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