Hobbes had already written a substantial draft of the Optical Treatise (Tractatus Opticus) in the late 1630s. The published version omits some of the more philosophical material, and only the first few pages are of philosophical interest, in connection with Hobbes’s theory of perception. The rest is highly technical; and Hobbes was immensely proud of it as his one major contribution to the new science — he believed he had done for optics, what Copernicus had done for astronomy, and Galileo for mechanics.

The structure of the work is modelled on Euclid’s geometrical method, with hypotheses, propositions, and corollaries. What is striking is the omission of a list of definitions, since his later works focus on definitions, to the almost complete exclusion of explicit hypotheses and numbered propositions.

It was published in Latin as the ‘Seventh Book of Optics’ in Mersenne’s Synopsis of Universal Geometry and Mixed Mathematics. . . . (Paris, 1644), pp.567–589. I have translated it from Molesworth, LW V, and page numbers in square brackets refer to that edition. I am not aware of any other translation into English.

Go to the Index to the Optical Treatise