Giving the players no meaningful choice is "railroading".
For the purposes of this discussion, I think this is a fair definition of "railroading". (I assume, for the record, that Ariosto intended to propose this as a definition and not just as an example.)
I will also add, because I think it is helpful to be explicit about terms, that I believe there is a continuum between "railroading" on one end (where the PCs have no meaningful choices) and what I'll call a "sandpile" (where the GM is religiously strict about guiding the PCs in any way). In other words, it's not a binary matter. PCs can be given some meaningful choices without being allowed to make all possible meaningful choices. I hope everyone agrees that there are many points along this spectrum, even if we disagree about where on the spectrum we like to play.
As someone who likes plot, I'll also say that I prefer a game in which the PCs are given meaningful choices. To that extent, I'll agree with Ariosto that railroading is bad, in the sense that RPG experiences are more fun when there is a possibility of making meaningful choices.
However, I also need to agree with CharlesRyan's assertion that a plot does not necessarily have to be a railroad. We've certainly discussed plot with branch points, and I've read modules (Freeport Trilogy, War of the Burning Sky, for example) that unquestionably have plot, but also include many branch points and advice about how to handle the game even when it veers away from the expected path. I assume that everyone agrees that these adventures exist. Does anyone think that they don't have meaningful choice? Does anyone think that they lack plot?
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I'll take another example from the session I just finished. One of my PCs (the paladin) recently sacrificed her sword (one of the party's better magic weapons) to destroy an evil artifact and the character is very disappointed with the ho-hum replacement. Two other PCs want to help her out, and both independently decided to steal the new sword, leaving a crap sword as a decoy so the paladin doesn't notice while they're having the ho-hum blade enchanted better. The players thought this was hysterical and want to play out the farce of having one PC steal the other PC's decoy.
So now I have to figure out (essentially at the player's request) a sequence of events that will result in the desired hilarity. The players of both "good thief" characters told me their character's plans, so that part of the game is totally under player control. Even the idea of spending a session on this silliness was the player's idea. But they leave it in my hands to figure out the order in which their plans come off so the whole group gets to watch the delightful confusion.
Admittedly, how the next session ends is anyone's guess. But, in many ways, it's going to be very tightly plotted. I don't normally run many scenes in which everyone knows the conclusion, but there will need to be a lot of that to make the comedy reach its full extent. On the other hand, both the in-game schemes and the experience desired out-of-game came from meaningful decisions made by the players.
As far as I can tell, this is an example of a game with a lot of plot *and* meaningful decisions. I'm curious if anyone disagrees?
-KS