Analogy of the Sun

The first of the three great images of Republic VI–VII (with the Divided Line and the Cave). Just as the sun gives visible things their visibility and their growth, so the Good gives intelligible things their truth and their very being, and gives the mind the power to know them.

The comparison sets the Good “beyond being” in dignity and power — not itself one of the Forms but their source, as the sun is not sight but its cause. It is the seed of the Neoplatonic identification of the Good with the One.