Descartes's theories of light and vision were central components of his natural philosophy, closely linked to his cosmology, physics, theory of matter, and theory of perception. Descartes replaced traditional explanations of natural phenomena with explanations hidden under terms of matter and motion. By eliminating these theories, Descartes needed to formulate new explanations of the qualities of bodies and our perception of them. In other words Descartes goes on to call into question one’s ability to fully understand the things, which our eyes see. His work on optics focused on these questions.
In the discussion, Descartes draws a comparison between a blind man's abilities to understand the shape and sensations of objects, and our ability to understand an object's color with our sight. This raises the question of our senses' ability to interpret the world around us with accuracy.
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Inventions, which serve to increase its power, are among the most useful. Color: various ways in which bodies receive light and reflect it in our eyes
The differences a blind man notices between trees, rocks etc. do not seem any less to him than the differences between red, yellow etc. Thus: there is no need to suppose that something material passes from objects to our eyes to make us see colors and light, or even that there is something in the objects which resembles the ideas or sensations that we have of them.
You must think of rays of light as nothing other than the lines along which this action tends. Thus, there is infinity of such rays, which come from all the points of the luminous body towards all the points of the bodies it illuminates.
There are bodies, which break up the light-rays that meet them and take away all their force (black). There are others, which cause rays to be reflected, some in the same order at which they receive them (bodies with highly polished surfaces). Some bodies cause the rays to be...
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