Analogy of the Sun
The analogy of the Sun (or simile of the Sun or metaphor of the Sun) is found in the sixth book of The Republic (507b–509c), written by the Greek philosopher Plato as a dialogue between his brother Glaucon and Socrates, and narrated by the latter. Upon being urged by Glaucon to define goodness, a cautious Socrates professes himself incapable of doing so.[1]: 169 Instead he draws an analogy and offers to talk about "the child of goodness"[1]: 169 (Greek: "ἔκγονός τε τοῦ ἀγαθοῦ"). Socrates reveals this "child of goodness" to be the Sun, proposing that just as the Sun illuminates, bestowing the ability to see and be seen by the eye,[1]: 169 with its light, so the idea of goodness illumines the intelligible with truth. While the analogy sets forth both epistemological and ontological theories, it is debated whether these are most authentic to the teaching of Socrates or its later interpretations by Plato.