I assume it's easily yes, and I don't mean this strictly, just in theory. Only train against computers, then win the candidates and beat Magnus.

Consider other fields of endeavour.

For instance, you can watch cooking instructional videos all day and practice at home, and develop your skills to the point that you stun your friends and family with your culinary skills. It doesn't mean you could get up tomorrow and go to work in a fine dining restaurant, let alone become the head chef.

You could get pretty good just by playing against your computer, but not enough to reach a professional level.

that is a terrible analogy

Computers still have a very different style from humans. And it gets worse when you try to intentionally weaken them in order to train. Such a player would develop an anti-computer style that would not work against Magnus.

This thread should probably be moved into the low content thread just because it would get more notice there.

In a strictly literal sense the answer is of course no. To become world champion you have to win a world championship match against a human opponent, and to qualify for that match you have to win a candidate's tournament against other humans, and all the paths to qualify for the candidate's involve, you guessed it, winning chess games against humans.

So anyone who wins a world championship will, of necessity, have nonzero human competition by the time they get there.

If the actual question is about getting *good enough* to be world championship caliber purely through studying theory, playing computers, etc... then, well, the answer is still no in any practical sense but if you want to start getting into "technically anything is possible" philosophical territory it's less demonstrable I guess? But the answer definitely isn't "easily yes". It's effectively impossible, if not provably so.

So the scenario is basically:

Player X trains solely on computer until "ready"
Issues challenge of sufficient financial value to Magnus to risk his title
Magnus accepts and the title is on the line.

I'll stand against the thread and say it's not impossible, but it basically relies on that player being the one who was capable of winning the WC anyways. This particular training method might actually give you a better shot given that you'll have perfect information about Magnus' history while he'll have no idea of yours. This would be balanced by a lack of competitive experience/nerves.

I understand it's not a perfect analogy, but I think it conveys the main points, namely that
-just because you can develop a high level of skill in something in the comfort of your home doesn't mean you'll excel in applying those skills in a high-pressure environment,

-excelling at the highest levels requires more than just the raw skills of making good chess moves.

- there are differences in playing style between computers and humans, and it would take time to adapt.

That being said, it's an interesting question. If you compare other games, it's pretty clear that you could become world class in backgammon just by training with the computer. In poker you'd have no chance, since such a big part of the game is identifying and exploiting sub-optimal strategies in your opponents. Chess lies somewhere in between. You could get very good, but imo not reach a professional level.

Since the general consensus seems to be that it can't be done, another question perhaps might be what is the highest level you think somebody could reach without playing human competition?

I'm sure FM strength is attainable, though not easy
How about IM? 2500, 2600?

This is kind of the key point to what I thought about but didn't state clearly. There may be someone out there who could do it, but my belief is that person would essentially be an immense once in a generation talent overcoming a self imposed obstacle, and could become world champion more easily through a training program that does include human competition.

Which means there's not a definitive clear answer to this other than "not as strong as they could get without imposing an artificial limiting factor on their ability to progress.

When I started out in chess I was mostly playing against the computer and reading books from the library. When I started playing live tournaments my first rating was around 1600. That was during the time that computers were ridiculously weak, and even as a 1600 I could win some games against it.

These days with improved computers and lots more training material easily available you could get pretty good, but my sense is that there'd be a point where it would be hard to keep improving without actually testing yourself in competition to see your weaknesses. But you could get very good at tactics and develop a really strong opening repertoire, so that would take you some distance. 2200-2300/ low FM strength would probably be the peak.