Are good people still good if they don’t act in the face of chaos? Is there something awe-inspiring about people who do bad things, but who "are full of passionate intensity"? The question of how to tell good and evil apart – and whether they can be separated at all – is essential to the text of "The Second Coming."
Yeats’s generation had just witnessed the worst war in modern history (World War I) – one in which there were no "good guys," because every nation was sending its men to live for months in horrible trenches, often fighting over a few feet of land. The implication throughout the poem is that society has strayed too far from its values to act responsibly. The image at the beginning of the poem depicts a situation in which the falcon, a symbol of nobility and tradition, is "deaf" to the instructions of its master. "Innocence" is described as only a "ceremony," something that is put on for show, but perhaps not truly meant. "The best" people are said to "lack all conviction," which would seem to be a paradox. And the sphinx in the desert seems to embody a force that is neither good nor evil, but simply indifferent. By the end of the poem, the speaker’s question about what kind of "beast" is about to be born is merely the last sign of how far away society is from clear categories of "good" and "evil," compared to those found in the Bible.
The sphinx in the desert is best thought of as an inhuman force of nature. Therefore, it is neither good nor evil. It cares no more about the fates of people than does "the sun" that shines indifferently on everyone.