(By the way, in these posts I plan to discuss the entirety of the stories, which means that if you don't like to have plot elements revealed, you should not read here about stories you have not read.)
David G. Hartwell and Kathryn Cramer have offered a good basic summary of the ideas Le Guin is exploring in her story:
"The Shobies' Story" describes a society in which consensus matters more than individual viewpoints. [... It] posits a reality that emerges as the sum of what all the participants say: a meta-narrative, a democratically constructed myth. Le Guin tells us that the observer is part of the reality she's trying to describe. Every observer sees things differently, and the melding of those interpretations becomes the world.It's not just interpretations, though -- from the title to the final word, it is stories that create reality for her characters. Stories are dramatizations of interpretations, webs of cause and effect, and they are they are themselves subject to interpretations. "The Shobies' Story" becomes a kind of metaphor for science fiction: the characters are the first sentient beings to travel via a new, instantaneous space ship drive, and what they discover is that such travel requires them to get their stories straight. But the interesting thing here is not just that the new form of travel requires consensus reality, but that it requires consensus storytelling -- instantaneous travel through the universe relies on stories.
Now here's a passage from early in "Invaders", where a colonel is interrogating an alien who has landed a flying saucer in a football stadium:
"Our ships operate according to a principle of basic physics [said the alien, Flash]. Certain fundamental physical reactions are subject to the belief system of the human beings promoting them. If I believe that X is true, then X is more probably true than if I did not believe so."
The colonel leaned forward again. "We know that already. We call it the 'observer effect.' Our great physicist Werner Heisenberg--"
"Yes. I'm afraid we carry this principle a little further than that."
"What do you mean?"
Flash smirked. "I mean that our ships move through interstellar space by the power of prayer."
The prayer of "Invaders" is not much different from the stories of "The Shobies' Story" -- both require a shared belief. Travel through the universe, then, becomes as much a matter of faith as physics, and physics relies upon the faith, and, at least in "The Shobies' Story", the faith is much more powerful: conceivably, the characters could agree on a story in which they travel and arrive in any form they can imagine, and interstellar travel could then become an extension of wish fulfillment.
"Invaders" is very much about faith and wish fulfillment, much more than it is about interstellar travel, in fact. It is about cultural contact, too, and history and atrocity. And science fiction.
The structure is more complex than "The Shobies' Story", interweaving three narratives: 1.) events from the history of Pizarro's conquest of the Incas in the 16th century; 2.) the story of the aliens landing on Earth from 2001 to 2011; 3.) sections labelled "Today", in which a character a bit like John Kessel writes a story very much like the one we're reading. The Pizarro sections show the Incas' attempts to understand the invaders' God, and how the invaders' God provides a convenient excuse for murder, torture, dishonesty, theft, and greed. Some of these effects and excuses are mirrored in the invaded world of the early 21st century. Ultimately, one of the aliens offers what seems to be the most truthful statement of why events occur: "We do things for kicks." Escape from reality, too, is a fundamental desire: "Human beings cannot stand too much reality." Our desire for an escape from reality ("kicks") leads to the actions we commit.
This links the story of the invaders with some of the science fiction writer's musings about his profession:
It's not just physical laws that science fiction readers want to escape. Just as commonly, they want to escape human nature. In pursuit of this, sf offers comforting alternatives to the real world. For instance, if you start reading an sf story about some abused wimp, you can be pretty sure that by chapter two he's gooing to discover he has secret powers unavailable to those tormenting him, and by the end of the book, he's going to save the universe. Sf is full of this sort of thing, from the power fantasy of the alienated child to the alternative history where Hitler is strangled in his cradle and the Library of Alexandria is saved from the torch.There's a certain truth to such statements, but there's no need to assume the narrator is summing everything up for us and that we have found here The Message -- stories, faith, and escapism function in complex ways throughout the rest of "Invaders", suggesting that the kind of escapism people desire determines the kinds of stories they tell and the faiths they profess. Both "Invaders" and "The Shobies' Story" suggest that the stories we tell affect the reality we inhabit, but "Invaders" foregrounds the responsibility that storytelling then requires. Science fiction as described by the narrator is partially an evasion of reality, but also perhaps the creation of a dishonest reality.
Science fiction may in this way be considered as much an evasion of reality as any mind-distorting drug.
This explains the final section of the story, which melds all three of the sections. We have previously learned that the aliens are capable of time travel as well as space travel, but toward the end of the story one of the aliens reveals that he has lied about the nature of the time travel: "Our time machines take people to the past they believe in. There is no other past. You can't change it."
In the final section of "Invaders", the science-fiction-writing narrator ends up in South America just before the arrival of the Spanish, and he shares his knowledge with the Incas, leading to an extraordinary final sentence: "When the first Spaniards landed on their shores a few years later, they were slaughtered to the last man, and everyone lived happily ever after."
This is fun, of course, but Kessel's point is clear: such an alternate history is a wish-fullfilment power fantasy (the nerdy writer, described repeatedly in unheroic terms, travels into the past and is the savior of an entire civilization!) and a dishonest representation of reality -- it may be fun for some of us to believe that all the Incas needed was a well-informed skinny white guy, but our wishes will not change what happened. Denying what actually happened, denying what cannot be reversed with faith or fantasy, trivializes all that we know to be true. "Everyone lived happily ever after" is the clichéd tag line of a fairy tale. People who believe the world can be reduced to such fairy tales may end up committing or contributing to atrocities in their own world; worldviews affect the world.