Many historians of science have discussed mechanical philosophy as a central theme of seventeenth century science, especially focusing on the machine metaphor as a way of representing nature. Originally, this postulation was spawned by French philosopher René Descartes, who could see no difference between machines and natural bodies. Most previous studies have examined Descartes’ machine metaphor from only one perspective; their primary concerns were concentrated on the fact that Descartes tried to explain principles of nature by understanding natural objects through the analogy of mechanical objects because their mechanisms were more clearly recognizable than that of the natural objects.
In this paper, I will propose that Descartes pursued a more ambitious goal than simply attempting to gain a reasonable understanding of nature. His comparison of elements of nature with machines had an important role not only in the understanding of nature but also in Descartes’ other project, which involved constructing perfect machines by applying principles of nature in the construction of machines. In this paper, I will focus in detail on three types of telescopes that were presented in Descartes’ La Dioptrique and their theoretical principles, and thereby examine Descartes’ distinctive approach with similar aspects of modern scientific engineering. In La Dioptrique, Descartes regarded a telescope as an “extended eye”, which led to his development of a unique theory of the telescope. In addition to this theoretical consideration, Descartes expected that his theory of the telescope would contribute to improve contemporary telescopes.