Abstract

In 1604 Kepler published his Optical Part of Astronomy, dramatically changing the role of optics and the fundamental concept of vision. Instead of a window through which visual rays informed reason about its surrounding objects, the eye became a screen on which light painted images of no inherent cognitive value. The naturalization of the senses required a corresponding naturalization of the mind, which Descartes attempted to offer with a theory of the passions. Kepler’s optics turned sensations into purely causal effects, but the passions, indicators of benefit and damage to the individual, could provide them with meaning. This was a reversal of the traditional epistemological responsibilities of reason and the passions, and for Spinoza this demanded a reversal of their ethical and political roles. ‘Desire is the very essence of man’ he stated, and concluded: ‘society can be established … not by reason … but by threats.’