Alhazen’s Debt to Ptolemy’s Optics

Abstract

As it is currently imterpreted, the history of optics from its early Hellenistic beginnings to the dawn of the seventeenth century is divided into two major phases. The first of these phases saw the emergence of three distinct traditions of visual theory in Greco-Roman antiquity: (1) the “philosophical” tradition, which was rooted primarily in Platonic, Aristotelian, and Stoic doctrine, (2) the “medical” tradition, represented by the early Alexandrian physiologists and Galen, and (3) the “mathematical” tradition, whose greatest exponents were Euclid and Ptolemy. Each defined by its particular domain of concerns, these three traditions supposedly evolved along separate lines. Accordingly, while philosophical theorists pursued physical, psychological, and epistemological questions at the expense of anatomical, physiological, and mathematical ones, their medical counterparts subordinated philosophical and mathematical to anatomical and physiological considerations. And, finally, mathematical theorists tended to eschew all but ray-geometrical considerations in their search for visual explanations. For the most part, then, the three traditions developed not only in isolation from, but often in opposition to, one another.¹