Getting Biblical in Daily Life
The biggest subject Isaiah deals with is the wrath and the mercy of God. Even though Isaiah is most famous for its visions of peace—the wolf getting cuddly with the sheep, the lion chowing down on straw, etc. in Isaiah 11—God is persistently pretty wrathful throughout the whole of the book. His moments of peace and mercy are more like punctuation marks, coming at the end of long torrents of wrath. How can God's wrath be reconciled with his more merciful nature? It's a question Isaiah struggles to provide answers to.
Theologians in Judaism and Christianity have both claimed that God's wrath isn't really like God throwing a temper tantrum. He's not actually supremelymiffed, the way a human tyrant would be. God's arm striking down armies in wrath and so on is really a metaphor on the human level for a higher spiritual truth. It's more that human beings experience God as being wrathful when they put distance between themselves and him. It's not his real nature (which is merciful).
There's actually a good amount of evidence in Isaiah for this position. Most of the time, it portrays God as being a really, really angry and human-like God. But at other times, it suggests that God is hiding his face from his people, because they've turned away from him. It's this act of hiding, this absence, which is really what causes the wrath to happen. It's not God's presence which causes God's wrath, but his absence. Isaiah says, "Rather, your iniquities have been barriers between you and your God, and your sins have hidden his face from you so that he does not hear."
Overall, however, the big message seems to be that God's wrath is necessary because it purges out the wicked and the wasteful elements from what will eventually be a perfect group of people, free from war. Violence, now, is necessary only to make violence unnecessary later. It's not exactly the Mahatma Gandhi position on violence (which is total nonviolence at all times), but it's the model Isaiah is working with.
Isaiah uses an agricultural metaphor to make this point: "Dill is not threshed with a threshing sledge, nor is a cart wheel rolled over cumin; but dill is beaten out with a stick, and cumin with a rod" (Isaiah 28:27). The same way that dill and cumin need to get beaten with rods and sticks if they're going to be planted and yield more dill and more cumin, the Israelites need to endure God's wrath if they're going to be purified and live in peace on the Holy Mountain, producing more righteousness.