I would say there is more than a cheating history and a single game that triggered Magnus. However, most of it has a possible explanation. Like, I would be very nervous if you put me in front of a camera at 19 years. Are these arguments together strong enough? Hard to judge.
Do you have a link to this? Proof that this player has cheated in the past would be the strongest evidence, I believe, he'd do so again.
Having cheated in prior history is not a question, but the extent and recency of the behavior is.
Disclaimer: don't know much about chess, let alone professional chess.
I admit that it is a trickly problem, and I agree that Carlsen's behavior here is not beyond reproach. Withdrawing from the tournament only after having lost a game makes the statement much less impactfull since one can not discount the possibility that he's just being a rather sore looser. I would personally have respected his decision much more if he had followed his impulse (again, referred to in his statement) to withdraw as soon as Niemann had been invited to the tournament in the first place.
The interesting thing is the one party MORE qualified than Magnus and the other grandmasters to detect cheating is the chesscom statistics team and they think Hans has cheated online recently and didn't admit to it. Still, there's no smoking gun that proves the OTB matches were fixed, Hans can be innocent at least in those specific circumstances, but if he's been guilty in online chess recently is it truly fair to make the world champion play against him OTB?
>He wouldn't risk his whole reputation for nothing.
It is pretty important to realise in terms of Magnus's mindset he has given up on defending the world championship and doing anything other than achieving 2900 elo, the highest rating ever achieved. He is a champion, and that is his goal in life, he wants that rating in a way most people can't fathom. If he proves Hans Neimann is a cheater, Han's win's against Magnus are void, and Magnus's rating goes up. Imagine being the world champion and having your dream drift further away because of a known cheater beating you when they're at a disadvantage, what goes through your head? What goes through your head when you think of how many people COULD be cheating and making getting 2900 impossible? What can others do about the spectre of chess cheating, the world champion, doesn't stand up?
So what I'm saying here is, I wouldn't be super confident that Magnus wouldn't throw his reputation in the trash to become the greatest chess player who ever lived. I think he would absolutely throw away his reputation, but not for nothing.
Still people literally know the chesscom cheating team. IM Danny Rensch is the face. I would say there is a fair amount of respect for that team within the community, as well as a healthy scepticism. If anything they probably get more criticism for ignoring cheating than for taking action.
It’s a tough gig, chess cheating is very hard to prove.
That just shows that he is fallible, which I empathize with.
Also don't forget the bishop blunder by Nepo in the world championship against Magnus. That was a 1800 level blunder trapping the bishop. Nepo is in top 5 GM list.
The fact of the matter is that all GMs including Magnus have the potential to make blunders.
To be clear, I'm not saying this to make a claim that this is definitive proof of anything. I'm pointing out that the theory that Magnus simply blundered away the game doesn't hold water. Niemann had the advantage—as black no less—for essentially the entire game against someone who is widely known for being capable of grinding away nearly-perfectly for extensive periods of time.
Magnus only matched the top engine move 43% of the time, which is quite low for a super-GM. Hikaru said he'd bet money that it was Magnus' worst performance in any game in the last 3 years.
If the evidence shows that Magnus played badly, we do not have to jump to the conclusion that actually he was playing badly on purpose, for the intent of trying to detect a cheater. He himself wasn't even stupid enough to claim this.
No, instead, I am going to trust other grandmasters opinions that he was merely playing badly.
(Sorry for the dupe reply, too late to edit my other comment)
I agree but Magnus also plays bad games once in a while. So it is not quite clear from a sample size 1 and a std deviation of infinite.
There are a number of comments here which promote the idea that this is simply sour grapes by Magnus and totally uncalled for, and I find those perspectives to be overwhelmingly uncompelling.
Of course he played near-perfectly for 27 moves. That's what it means to be a 2700 (or even a 2500, if you think his recent ratings growth is the product of cheating). Virtually any high-level game will look like that - the players playing mostly perfectly, with on average one or two significant mistakes, but sometimes not even that.
No more evidence is required. The quality of Hans Niemann's moves, recently as well as during his rise from 2400-rating three years ago, is enough evidence against him.
Either he is a good as Stockfish, or ...
Here is the first interview I could find from a 10 second google:
https://www.dw.com/en/world-chess-champion-magnus-carlsen-th...
The money quote:
" My practice at home is with the computer. When I study chess with other people, we always have a chess board. But on my own, it's always at the computer. "
Dude probably trains with computers regularly. He has a better memory than 10 average Joe's combined. He's been the absolute #1 of the world for what, 10 years now?
He wouldn't risk his whole reputation for nothing.
I personally take his suspicions very seriously, though I agree that evidence has to be presented sooner or later.