Epigraphs are like little appetizers to the great entrée of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
How much does a man live, after all?
Does he live a thousand days, or one only?
For a week, or for several centuries?
How long does a man spend dying?
What does it mean to say "for ever"?
PABLO NERUDA
The epigraph comes from a poem by Chilean Nobel laureate Pablo Neruda, one of South America's most famous authors and probably the inspiration for the character of the Poet in Allende's novel. Neruda is, first and foremost, a great poet, and his works have been translated into oodles of languages and read by people all over the world. But he's also intimately associated with Chile and with Chilean politics. He was a member of the Chilean Communist Party, and some of his poems are pretty revolutionary. He died only twelve days after the violent military coup that put an end to democracy and leftist politics in Chile for almost two decades.
So what's one of Neruda's poems doing as the epigraph to The House of the Spirits? Well, for starters, it's our first major clue to the setting of the novel. Allende never comes out and says it, but it's clear that the story takes place in Chile (more on the setting later). And, since you could argue that national identity and politics are pretty important to many of the characters, starting the novel off with a quote from a hugely famous and recognizable Chilean poet is a big hint about where all this action goes down.
But aside from giving us some context, the epigraph also provides an idea of some of the important themes in the novel. These particular lines of verse have something to do with life, death, and immortality. When the speaker asks, "How much does a man live, after all?" and "How long does a man spend dying?" he's probably not looking for the average lifespan of the Chilean male (so, yes, 73.69 years would be kind of a smart-aleck answer). This is poetry, which means it's more complicated than that.
What he really wants to know is probably more along the lines of: "What's the whole point of living and dying anyway?" "What do we accomplish in our lives, and how do people remember us when we die?" Which brings us to the all-important theme of MEMORY! You'll notice that it comes up a lot in The House of the Spirits. Maybe memory is one of the ways we can say something – or someone – lasts "for ever."