“Walk in the light of your fire.” This is irony; sarcasm, to get people to think about their actions. The desire of God, of course, is that people would not walk in the light of their own fire. The prophets sometimes used irony to get people to think about what they were doing, as long as it was clear from the context and subject matter that the prophet’s words were indeed irony. For example, Amos said, “Go to Bethel, and sin.” Bethel had become a center of the worship of pagan gods, but Amos was certainly not encouraging people to go and sin, he, like Isaiah, was using irony. Amos and Isaiah were contemporaries.