I had been a passionate reader of science fiction for a few years before I became, in high school, a passionate fan of the Pink Floyd album The Wall. My passions have shifted over the years, of course, because each year brings different books to read and different music to listen to, and experiences can't help but etch contours into our aesthetics. Shadows of the old passions linger, though, casting themselves across the ever-expanding landscape of memory. I find now that when I think about science fiction, I also think about walls, about borders and barriers, about things sheltered, barricaded, delineated, excluded.

The English language stole "wall" from Latin, washing out its meaning in the process. To a Roman, a wall (vallum) was a rampart constructed from stakes (vallus), a defensive structure.

Vallum was also a term used for the earthen fortification behind Hadrian's Wall, which the Romans began building in 122 to defend against various groups, particularly Celtic tribes. The wall took about ten years to build, and covered seventy-three miles. Portions remain today and are some of the most popular tourist destinations in northern England. Other portions ended up being used over the centuries to build houses, roads, and other walls.

The Latin word for "wall" in the sense we know was murus, from which come the English words "mural" and "immure" (to imprison or entomb between walls). "Interval" derives from intervallum, "between the ramparts," while "intramural" comes from adding the Latin prefix intra (within) to murus: "within the walls."

Demolition of the Berlin Wall began in 1989. The president of East Germany, Erich Honeker, resigned on October 18, one day after my fourteenth birthday.

At the beginning of Theodore R. Cogswell's story "The Wall Around the World," the protagonist, Porgie, is fourteen, "an age that tends to view the word impossible as a meaningless term invented by adults for their own peculiar purposes."

I stopped reading science fiction sometime during college. I had read less and less of it as I made my way through high school, replacing it with Modernists and playwrights, and so it wasn't a difficult addiction to give up. Indeed, it took me a while to realize that I had given anything up at all.

I stopped listening to Pink Floyd during college, too.

Though I never returned with much fervor to Pink Floyd, I did return to science fiction, but not in the way I had when I was younger. My interest was less in traditional science fiction than in writing that hovered over borders between different genre definitions. I am attracted to surrealist imagery, to language that revels in its own artifice, to imagination. I didn't want to keep looking at the same old walls.

There are, it seems to me, two worlds of fiction. There is the world within the walls of a specific type of fiction, and there is the world outside the walls. Intramural writing doesn't press against the walls, though it might repaint them now and then, or add new bricks to plug a leak. The writing that lives between the ramparts, though, that seeks unstaked territory, must build its own structures every time it desires shelter. Having built them, such writing is free to renovate the structures, expand on them, pillage them, destroy them, abandon them.

It is the latter type of writing that brought me back to what I thought was science fiction, though I realize now it was only science fiction under the most liberal definition of the term, one with porous walls. I moved from enjoying the confines of the fort that is traditional science fiction to finding the walls oppressive or monotonous or so familiar that all they could sustain was contempt.

In July of 1990, former Pink Floyd band member Roger Waters, who had written most of The Wall, staged a live performance of the album at Potsdamer Platz, which was then essentially a no-man's-land between the two halves of Berlin. A few critics noted that the connections between the Berlin Wall and the concept of the Pink Floyd album were tenuous, if not contradictory—the album is about trying to keep things out, while the purpose of the Berlin Wall was as much to hold people in.

I listened to part of that concert on the radio. It was the first time I had ever heard the songs. Not knowing anything about The Wall or Pink Floyd or Roger Waters, I couldn't make sense of much of it, but I vividly remember Sinead O'Connor singing "Mother."

I also remember that as I listened to The Wall live from Berlin, I was paging through an old issue of Galaxy magazine that I had gotten at a used bookstore.

Growing up in New Hampshire, it was impossible to escape the influence of Robert Frost. My grandfather maintained that the poem "Brown's Descent" took place on Bridgewater Hill, where he and my grandmother lived during most of my childhood. Early in the twentieth century, Frost taught for a few months at Plymouth State College, where my mother has worked for thirty years. My father and I once drove our motorcycles to the Frost Farm in Franconia. I don't think a year of elementary school went by where we weren't required to memorize one of Frost's poems.

I have no idea when I first heard the famous opening line of "Mending Wall" ("Something there is that doesn't love a wall. . ."), because I feel like I've always known it and always thought it was a self-evident truth. Discussing science fiction with people who want it to remain a genre, a thing with clear borders and strong walls, I feel like Frost's narrator, who gets frustrated with a stubborn man who says, "Good fences make good neighbors," and thinks that is enough. "Why do they make good neighbors?" the narrator asks, then says:

Before I built a wall I'd ask to know
What I was walling in or walling out,
And to whom I was like to give offense.
Something there is that doesn't love a wall,
That wants it down.

When I first returned to reading what I thought was science fiction, I decided I wanted all the walls to come down. I liked the view from outside, and so I thought everyone would, and if they didn't, they deserved to choke to death on the stagnant air in their immured imaginations.

Then I realized that most of what I enjoyed in fiction, most of what excited me, could not under any definition be called "science fiction." It was philosophical romance, or literary fantasy, or slipstream, or surrealism, or meta-decadent post-structural fabulation, or whatever other label happened to get smeared on its bootless soul. It was a tendency, not a genre. It was Kafka and Borges and Jose Saramago; it was Angela Carter and Kobo Abe and Toni Morrison; it was Jack Vance and Cordwainer Smith, M. John Harrison and China Miéville, Jeff VanderMeer and Kelly Link; it was Trampoline, Polyphony, Leviathan, Mojo: Conjure Stories. It certainly wasn't anything new, because this tendency goes all the way back to the fables told by the first sentient humans to sit beside a fire and wonder at the vastness of the universe. Compared to this tendency, kitchen-sink realism is a minor deviation, an outbuilding of a castle, and genrified science fiction is its equally walled-in neighbor. Both are nice places to visit, but neither should be mistaken for the entire kingdom.

Most of the Great Wall of China is about thirty feet high. It could always be scaled by determined people, but the plan was for it to be tall enough that horses couldn't jump over, and thus the wall would prevent nomadic tribes from crossing into the Empire's territory to wreak havoc or run off with valuable property. Today, parts of the wall have been preserved for tourists, but other parts have suffered various fates, and in some places, stones have been taken from the wall to build houses or other structures, to repair roads, or to serve as souvenirs. Certain sections have been shattered by bulldozers so that new projects could begin.

Walls can, of course, be necessary and useful. But they suffer erosion, entropy, and obsolence as much as any other object. Something there is that doesn't love a wall, no matter how great it is.

The climactic moment of the Pink Floyd album arrives when a crowd shouts, "Tear down the wall! Tear down the wall!" Then comes the sound of bricks and stones cracking, crumbling, collapsing. The last words are sung quietly over the settling rubble: "After all, it's not easy banging your heart against some mad bugger's wall."

Those once seemed like profound words to me. Now they seem, depending on the intonation, self-pitying or grandiose.

Maybe the best thing to do with an old wall that is no longer useful or necessary is to break it apart and use the stones for other things. Otherwise, all that's left is a roadside attraction or a museum. A fine enough fate for an artifact, but not for a style of art.