> Not sure what the claim about guessing means.
By "guessing" I meant the opposite of "trickery". The latter, I remind you, you described as meaning, "basically, already know the answer." I hope you'll concede that "guessing" means not already knowing the answer. I'm not using those terms to prove a point or persuade you of anything, just for convenience: "guessing" saves me from typing out the phrase "psychological skill, manipulation, perception, or other mental techniques" and "trickery" for "gimmicks, trick pens, hidden cameras, confederates, sleights-of-hand, etc."
So, what we're (I think) arguing over is whether any mentalism tricks rely on "guessing" as opposed to "trickery". Obviously, they all typically claim to be based on "guessing", that's sort of the definition of mentalism as opposed to other kinds of stage magic. But my position is that some subset of such tricks really are based on that, and I believe your position is the opposite, that they're all what we're calling "trickery." If I've misunderstood, please feel free to clarify.
I looked for a few more examples (all by Derren Brown, not because I think he's unique but because he is prolific and practically all of his stuff is on youtube). One I already mentioned; another is the routine he does with Stephen Merchant; another is the one where he does the "Russian scam" on strangers; and a fourth is the bit where he tries to buy jewelry with blank paper rather than money. My understanding of your position is that these must involve "trickery" - the people involved are actors, there was sleight-of-hand the camera didn't show, or some other gimmick. I think he really is just conning those people.
As for the books: compare to difficult-but-not-impossible sleights, like a perfect Faro or dead-cutting the Nth card. How many magic books have a trick requiring a Faro shuffle? Not many, because it takes a lot of practice to do reliably. And yet, there are (I think!) tricks being performed on stage which do rely on it. Same thing here, except that, unlike Faros and dead cuts, tricks based on "guessing" generally can't be practiced without an audience. "Go perform this pick-the-envelope trick in restaurants and shitty nightclubs, over and over, failing repeatedly, getting booed off stage, until you finally learn to do it reliably, and then there you are!" would not be very useful to the budding mentalist! But it doesn't follow that it cannot be done.
And as for why we're arguing, well, I just like the kind of discussion where a casual belief of mine (something I think is true, but haven't done any particular research in to) is challenged - I think they are useful and good and worthwhile. I'm not angry or trying to show you up or "win", whatever that might mean in this context. Totally ready to update my own beliefs on all this. There are at least two tricks I used to think were probably "guesswork" before this thread, which I re-watched with more skeptical eyes and now believe are "trickery". But as I listed, there also still others that I think aren't.