The sun is a symbol, in this poem, of the beauty and power of life and nature. The sun is eternal and bright, and looks down on the whole world all at once. In this poem, the sun rules the land of the living, and when you die, you leave the sun behind forever. It’s important to note that, even though the sun is a symbol of life, it isn’t alive. The poem makes a big deal out of the eternal life of the sun, as opposed to the brief life of humans.
- Line 18: In this line, the absence of the sun is the first sign of death. When the sun can’t see you anymore, your life is over. Notice how the speaker calls the sun "all-beholding." That just means it sees everything in the world all at once, like some kind of giant eyeball – only less Sauron-creepy than that.
- Line 38: Here, when the speaker is trying to tell us how old the hills are, he compares them to the "ancient" sun. This reinforces the importance of the sun, watching over everything in nature, as old as anything in the world. In a way, the sun seems almost god-like, although the poem never comes out and says as much.
- Line 45: One more cameo by the sun. Again, it’s in a powerful position. It's a beautiful, "golden" force "shining" down on the "sad abodes" below. In "Thanatopsis" the sun is always separate from the world of death and sadness and fear that humans live in. It’s a symbol of everything unchanging and pure and eternal.