A quotation from Act IV, Scene 1 of Shakespeare's King Lear. The complete idea is "As flies to wanton boys, are we to the gods. They kill us for their sport," which is spoken by Gloucester after his life has gone to pieces; he's cast out his trustworthy son Edgar and trusted his bastard son Edmund, who turns out to be conspiring against him and has gotten Gloucester blinded as punishment for treachery that Gloucester didn't commit. At the point of this speech Gloucester is about to attempt suicide.