Yeats’s speaker sounds tired of thinking. He longs to be like the dawn: something that has witnessed human ingenuity and ambition but never cared about them. The dawn has looked down on an old queen measuring a town with the pin of a brooch, and on withered Babylonian astronomers who watched the planets and then sat down to do sums. Neither act moves the dawn. It simply goes on being beautiful and detached, lightly rocking a glittering coach above the shoulders of the horses. For the speaker, all that learning and measuring is worthless—“no knowledge is worth a straw.” What he wants instead is the dawn’s freedom: ignorance and wantonness, a life unburdened by meaning.
The mood is wistful and a little defiant, dreamy rather than bitter.