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Philosophical Science

Mirror, Mirror

Tim Wilkinson reflects on an old question.

Why do mirrors reverse left with right but not up with down?

It’s a problem with a long history. Plato addressed it in his dialogue Timaeus in the Fourth Century BCE, but was somewhat hampered by the prevailing theory of vision. Following Empedocles, Plato thought sight is explained by rays emitted from fire in the eyes. To account for the fact that we can’t see at night, Empedocles suggested that there must be some interaction between the rays emanating from the eyes and those emitted by other fires, such as the sun. The theory that sight is the result of an external influence entering the eyes was proposed by Aristotle somewhat later.

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