Some say the world will end in fire, Some say in ice.
OK, everyone. Line up. If you think the world will end in fire, stand to the right. If you think it will end in ice, move to the left. Let's put this to a vote.
The poem begins with this kind of polite difference of opinion. Nonetheless, the two groups are separated by a line break, to illustrate their disagreement. They can't even stand to be on the same line!
We don't learn who exactly takes each side. The two sides are anonymous, fluid groups of people.
The great Fire vs. Ice Debate is not one we've heard of before. So we must be dealing with symbols.
In a poem this short, you have to question absolutely everything. Take nothing for granted.
For example, what does "the world will end" mean? Is the speaker talking in Biblical terms about the Apocalypse? Or is he imagining natural or man-made disasters, like whether we'll blow ourselves up or die out in another ice age? Or does he mean "world will end" in a more personal sense, like the way his world will end, or your world?
At a literal level, fire and ice are both ways that the human species could be extinguished. There are almost infinite possibilities for either one to happen. For example, a giant comet hitting the earth and making it explode: fire. A slightly less giant comet hitting the earth and creating a huge cloud of ash that blocks the sun: ice.
Thinking outside of the "natural catastrophe" box, "fire" and "ice" could also represent different kinds of human emotions. Some philosophers, for example, have divided the human soul into "rational" and "animal" components, where the "rational" is cool and deliberate, while the "animal" is hot and hasty.
If you get in a yelling match with one of your friends and suddenly get so angry that you slug them, that's fire. But if you despise one of your enemies so much that you make a deliberate, painstaking plan for their downfall, that's ice.
At this point you might be thinking, "Hey, Shmoop, aren't you making this all too clear-cut? Maybe fire and ice aren't total opposites. Maybe they can exist at the same time and even interact with each other." At which point we'd have to turn in our keyboard and hand you the keys to the Kingdom of Shmoop.
The whole "fire and ice" dispute is based on speculation, because nobody has any idea how the world will end. For such an intense topic, the idea of weighting options in a rational manner seems strange and even absurd. The speaker talks about options for the end of the world as if he were holding up different yogurt brands at the supermarket. ("Hm. Looks like 'ice' has less calories!")
From what I've tasted of desire I hold with those who favor fire.
Maybe our yogurt comparison wasn't so far off, after all. The speaker has sampled "desire," a "hot" emotion, so he's going to line up with the folks who think fire will end the world. He knows how powerful it can be.
The word "tasted" implies that he hasn't felt the full brunt of fire's energy – he has only gotten a small sample, like those little bite-sized portions of food that they hand out at grocery stores.
To put it another way, think of the character Cyclops from X-Men. Cyclops wears those sunglasses all the time because they control the energy that shoots out of his eyes. If he were to take them off permanently, they would burn up everything around him. He prevents this mass destruction by focusing the energy. The speaker suggests that we do the same thing with emotions like "desire." We keep them on a leash so we don't lose control. If conditions arose that caused us to lose control…watch out.
"Desire" is considered "hot" because it always relates to the body in some way. The most obvious example is romantic or sexual desire. Sure, love is warm and fuzzy, but sex, jealousy, and desire can run out of control.
The speaker knows about this unstable side of our "hot" emotions. He has been around the bend and acquired worldly wisdom along the way. He's a voice of experience and not just some naïve kid who has only felt puppy love.