Like most of Shakespeare's plays, Yeats' "The Second Coming" is written in blank verse, i.e., unrhymed iambic pentameter. The lines you get backwards, Meself, are as follows:


The best lack all conviction, while the worst

Are full of passionate intensity.


In a sense, that's true: The best and the brightest are aware of nuance, shading--to them the world is not all black and white. The worst, on the other hand, see only absolutes--good and evil, with us or against us. Yeats, when he wrote the poem, was drawn to fascism--the "rough beast, slouching towards Bethlehem," was fascism, reacting to the decadent society
he describes in the first half of the poem; before he died, he had begun to recognize the horror that fascism is in reality.

Charles