From Sundials to Pendulum Clocks

Plato’s theory of knowledge is summarized in one of his most famous myths, that of the cave [1, VII, 514–517]. In it, he proposes that we imagine some captives who, chained in such a way that they cannot move, have lived since childhood in an underground cave whose frontier wall is their only world. Behind them, objects and beings pass by along a steep path, and still further back a fire illuminates them and projects on the wall the silhouettes of what is passing between the fire and them. If we freed these captives from their chains, they would have the opportunity to abandon their ignorance that makes them consider the shadows on the wall as the only reality, since turning around they could contemplate the fire that makes them possible and the realities of which they are a projection.