Analogy of the Sun
|This article relies on references to primary sources. (November 2013)|
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The Metaphor of the Sun (or, Simile of the Sun) is found in The Republic VI (507b–509c), and was written by the Greek philosopher Plato as a dialogue between Glaucon (Plato's elder brother) and Socrates (narrated by the latter). Upon being urged to explain the idea of goodness, a cautious Socrates doubts his ability to do so. Instead he offers to talk about its ‘offspring’ (506e). Socrates reveals this ‘offspring’ to be the sun, proposing that just as the sun illumines the visible with 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.
Socrates says that the sense of sight is unusual. He argues that for the other senses to be used all that is needed is the sense itself and that which can be sensed by it. (e.g., to taste sweetness, one needs the sense of taste and that which can be tasted as sweet) The sense of sight, however, needs something additional, namely light, in order to see that which is visible. Both the sense of sight is able to see and that which is visible can be seen when light is present but of course not when absent. Socrates exclaims “Then with no slight idea have the sense and the power of being seen been united by a more precious bond than the other pairs!—unless light is quite without worth.” (507e-508a)
Having made these claims, Socrates asks Glaucon, “…which of the gods in heaven can you put down as cause and master of this, whose light makes our sight see so beautifully and the things to be seen?” (508a) Glaucon responds that both he and all others would answer that this is the sun. Analogously, Socrates says, as the sun illuminates the visible with light so the idea of goodness illuminates the intelligible with truth. Also, as the eye’s ability to see is made possible by the light of the sun so the soul’s ability to know is made possible by the truth of goodness.
Understand then, that it is the same with the soul, thus: when it settles itself firmly in that region in which truth and real being brightly shine, it understands and knows it and appears to have reason; but when it has nothing to rest on but that which is mingled with darkness—that which becomes and perishes, it opines, it grows dim-sighted, changing opinions up and down, and is like something without reason. ('The Republic, VI - 508d; trans. W.H.D. Rouse)
The allusion to "…that which becomes and perishes…" relates to all of that which is perceived by the bodily senses. The bodily senses make it clear that all visible things are subject to change, which Socrates categorizes into either the change of becoming or the change of perishing. Conveying an underlying assumption that true knowledge is of that which is not subject to change, Socrates argues that the bodily senses can only bring us to opinions.
Instead, Socrates continues, knowledge is to be found in "… that region in which truth and real being brightly shine…" (508d) This is the intelligible illuminated by the highest idea, that of goodness. Since truth and being find their source in this highest idea, only the souls that are illumined by this source can be said to possess knowledge, whereas those souls which turn away are "…mingled with darkness…". This subject is later vividly illustrated in the Allegory of the Cave (514a-520a), where prisoners bound in a dark cave since childhood are examples of these souls turned away from illumination.
Socrates further asserts that as the sun makes the generation, growth and nurture of that which is visible possible, so the idea of goodness makes the knowledge of that which is intelligible possible:
- The sun provides not only the power of being seen for things seen, but, as I think you will agree, also their generation and growth and nurture, although it is not itself generation…Similarly with things known, you will agree that the good is not only the cause of their becoming known, but the cause that they are, the cause of their state of being, although the good is not itself a state of being but something transcending far beyond it in dignity and power.
Incidentally, the metaphor of the sun exemplifies a traditional interrelation between metaphysics and epistemology: interpretations of fundamental existence create — and are created by — ways of knowing. It also neatly sums up two views for which Plato is recognized: his rationalism and his realism (about universals).
- The Republic VI (509b); trans.[W.H.D. Rouse])