Images are significant in Epicurean philosophy for the light they shed on Epicurus' theory of how we receive information about the outside world. There is a long discussion in Book 4 of Lucretius on this topic. Although our understanding of light and hearing and other sensations is much different today, the discussion of images shows that Epicurus understood the nature of illusions and other distortions in the information we perceive about the outside world, and therefore the necessity of adjusting for those distortions.
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