Descartes’s most extensive discussion of the law of refraction and the shape of the anaclastic lens is contained in Rule 8 of "Rules for the Direction of the Mind". Few reconstructions of Descartes’s discovery of the law of refraction take Rule 8 as their basis. In Rule 8, Descartes denies that the law of refraction can be discovered by purely mathematical means, and he requires that the law of refraction be deduced from physical principles about natural power or force, the (...) nature of the action of light, and the behavior of light rays in a variety of transparent media. For over a century, however, there has been broad agreement that Descartes discovered the law of refraction by purely mathematical means, and that he only later provided the relevant physical rationale (via comparisons or analogies) in Dioptrics II. I execute each step in Descartes’s proposed deduction of the law of refraction and the shape of the anaclastic lens in Rule 8 and concretely show how Descartes could have discovered the law of refraction and the shape of the anaclastic by its means. Rule 8, I argue, reflects Descartes’s actual path to the discovery of the law of refraction and the shape of the anaclastic lens. (shrink)

In this paper I address Descartes’ use of analogy in physics. First, I introduce Descartes’ hypothetical reasoning, distinguishing between analogy and hypothesis. Second, I examine in detail Descartes’ use of analogy to both discover causes and add plausibility to his hypotheses—even though not always explicitly stated, Descartes’ practice assumes a unified view of the subject matter of physics as the extension of bodies in terms of their size, shape and the motion of their parts. Third, I present Descartes’ unique “philosophy (...) of analogy”, where the absence of analogy serves as a criterion for falsifying proposed explanations in physics. I conclude by defending Descartes’ philosophy of analogy by appeal to the value scientists assign to simplicity in their explanations. (shrink)

Descartes is usually taken to be a strict reductionist, and he frequently describes his work in reductionist terms. This dissertation, however, makes the case that he is a nonreductionist in certain areas of his philosophy and natural philosophy. This might seem like simple inconsistency, or a mismatch between Descartes's ambitions and his achievements. I argue that here it is more than that: nonreductionism is compatible with his wider commitments, and allowing for irreducibles increases the explanatory power of his system. Moreover, (...) Descartes depends on nonreductionist knowledge and on irreducibles in order to maintain his epistemology and metaphysics. That is, there is more in the Cartesian world than mind, matter, and God. (shrink)

I argue that Descartes explains physiology in terms of whole systems, and not in terms of the size, shape and motion of tiny corpuscles (corpuscular mechanics). It is a standard, entrenched view that Descartes’ proper means of explanation in the natural world is through strict reduction to corpuscular mechanics. This view is bolstered by a handful of corpuscular–mechanical explanations in Descartes’ physics, which have been taken to be representative of his treatment of all natural phenomena. However, Descartes’ explanations of the (...) ‘principal parts’ of physiology do not follow the corpuscular–mechanical pattern. Des Chene has identified systems in Descartes’ account of physiology, but takes them ultimately to reduce down to the corpuscle level. I argue that they do not. Rather, Descartes maintains entire systems, with components selected from multiple levels of organization, in order to construct more complete explanations than corpuscular mechanics alone would allow. (shrink)

Analogies between hearing and seeing already existed in ancient Greek theories of perception. The present paper follows the evolution of such analogies until the rise of 17th century optics, with due regard to the diversity of their origins and nature but with particular emphasis on their bearing on the physical concepts of light and sound. Whereas the old Greek analogies were only side effects of the unifying concepts of perception, the analogies of the 17th century played an important role in (...) constructing optical theories by imitation of acoustic theories, or vice versa. This transition depended on several factors including the changing relations between optics, music, mathematics, and physics, the diversity of early modern concepts of sound, and the rise of a new physics based on experimentation and mechanical explanation. (shrink)