The Sun Simile
February 28, 2026 – 11:43 pmPlato’s simile in Republic 508-9 can be summarised as follows:
| The Form of the Good | The Sun |
| Intelligible world | Visible world |
| Source of Truth or Reality(508e) Yields (508e) 1. Truth or reality to intelligibilia 2. Power of knowing to mind Thus (508e) 1. Not knowing but cause of knowing 2. Known by the knowing it causes |
Source of light (508a) Yields 1. Visibility to sensibilia (507e) 2. Power of seeing to eye (508b) Thus (508b) 1. Not seeing but cause of seeing 2. Seen by the seeing it causes |
| Causes reality of objects of knowing But is not that reality (509b) |
Causes processes of growth But is not such a process (509b) |
| Deprivation results in (508d) 1. No truth or reality (= change/decay) 2. Poor intelligence (= opinion) |
Deprivation results in 1. No light (508c) 2. Poor sight (508d) |
In the simile, note two stumbles.
- If light yields visibility to visible things, then it would be more natural to say that the Good is responsible for the intelligibility of the intelligible, rather than the truth or reality of those things.
- The claim that the Sun is the source of light and the Sun causes the processes (genesis) of growth is not a match to the claim that the Good is the source of Reality and the Good causes the reality of knowable things. The ‘coming into being’ of natural things is not like the unchanging being of the knowable things.