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Caustics are the brightest places in an optical field. They are the singularities of geometrical optics. The most familiar caustic is the rainbow, a grossly distorted image of the Sun in the form of a giant arc in the skyspace of directions, formed by the angular focusing of sunlight that has been twice refracted and once reflected in raindrops.

— René Descartes

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More quotes by René Descartes

In order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.

Principles of Philosophy (1644)

I was not, thank heaven, in a condition which compelled me to make merchandise of Science for the bettering of my fortune.

I suppose the body to be nothing but a statue or machine made of earth, which God forms with the explicit intention of making it as much as possible like us.

Le Homme (The Treatise on Man) (1662)

If you would be a real seeker after truth, you must at least once in your life doubt, as far as possible, all things.

The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge.

Key Philosophical Writings (1997)

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