I was lurking around on rpg.net and saw this thread about railroading, and I decided to read through it because the topic interests me. The thread inevitably devolved into pointless argument about terminology, as all such threads on just about any forum I've ever seen do, but why? Why can't gamers discuss the concept of "railroading" (or its close cousin, variously termed "DM illusionism", "the quantum ogre", or "Schrödinger's dungeon", wherein the DM cleverly hides the fact that he's railroading the PCs by quietly moving encounters into their path, regardless of the path that they "choose") without the discussion turning into empty wankery about what all the participants mean by words like "railroad" and "agency" and "DM"?
And I think that I've had a sudden realization that explains it: most gamers cannot have a coherent discussion about railroading because most gamers are playing games (or maybe a better way of putting it would be "most purported role-players are participating in activities") where railroading is not inherently verboten and doesn't really have a reason to be. Simply put, most hobby-gamers aren't actually playing role-playing games in the strict sense, where choices matter and the GM isn't just pulling their strings like a maestro puppeteer.
Only the OSR folks are actually gaming, actually role-playing in the strict sense—and so it's only within the context of OSR-style games (a sandbox that the referee creates beforehand and then does not fuck with just because the players do something unexpected) that "railroading" is even a coherent concept. In an old-school sandbox, if the players decide to leave town, travel north-northwest, and explore map-hex G32, the diligent referee has already presumably put something in hex G32, and that's what the players find; or maybe there's nothing interesting there, and if that's what they find, that's okay too. It was their choice to go there and explore that location.
The world is the world, once the game has officially begun. But if the ref decides to move the contents of hex B12 into hex G32 because it would be more interesting for the players to encounter something really cool… well, no, just no, that's not a role-playing game anymore—because the players' choice of where to go and what to do has been totally abnegated by the referee, and if you can't make a choice then you can't play a role, period.
The fact that the referee always technically has the power to undermine player agency is an unavoidable side-effect of the game's structure: role-playing games are built around players interacting with an imagined world run by a neutral referee with final authority over said world and its rules. And game referees are human, so the temptation to let that one world—"neutral"—be quietly forgotten is strong. After all, wouldn't be so cool and so fun for the players to play through the epic story you envision? And it's not like they'll ever know… so what's the harm?
These are the fiendish whispers heard in the deep, dark recesses of every referee's mind. But they offer false promises and foul temptations, and they must be resisted at all cost. Pour wax into thine ears, O thou Ulysses of the polyhedral dice, and heed not the sirens' song! Thy power over thy game is awesome—and all too often, to exercise it at all is to abuse it.