In theory, but that would be more in the realm of philosophy. You can think hard about something you already know and deduce knew knowledge from there, but you would have no way of confirming that knowledge or putting it to a test.

In short, you end up like the ancient Greeks who could come up with a bunch of hypothetical statements, and could only assume that they were correct.

I think you could make a case that you could learn new forms of pure math if you had a method of storing information in your brain.

You need to read Asimov’s The Last Answer.

Philosophically speaking, “rationalism” is the acquisition of knowledge through reason alone without external stimuli.

E.g. one could come to new knowledge about maths by just reflecting on axioms

Requires external stimuli. The human brain is kind of designed to take in lots of information and process it. Interact with things etc.

You’re asking the unknowable.

Not that we can’t play along and have some fun, but that’s all it is.

I think the important part of your question comes down to what you could learn, rather than if.

Consciousness, in part, requires a progression of thought. Meaning that you have one thought, it resolves, the next thought arises, and so on. There’s an arrow of time to it. So, each thought along the way is a form of learning. It is, however, a limited form because you’re limited in scope. If the only perception possible is self perception, you can learn as much about your self as there is self to learn.

Without stimuli, a perception of external things, you can’t learn anything other than the self. There might as well not be anything but the self when you have no way of interacting with it.

Now, if you want to play woowoo with it, you might think, in this formless state, and by thinking discover that you have new ways of perceiving things, new senses in a sense. Or perhaps that you have to learn how to perceive whatever state surrounds you with your previously existing senses in a similar way to how someone that goes blind has to relearn how to use their other senses in the absence of sight. It isn’t so much that the senses no longer exist, but that the mind has to adapt to entirely new signals that it hasn’t figured out yet.

Past memory isn’t necessary to learn new things in your hypothetical state, only the ability to form new memories.

Sitting wherever you are now, close your eyes, swaddle yourself up in a quiet space. Let yourself think with as little stimulation as possible by partially blocking your senses and making what’s left as uniform as possible. In that state, the only changing stimulus (as a thought experiment) is your mind so long as you stay still.

We still learn in a state like that. Sensory deprivation as a form of meditation and inner exploration exists. And you can learn in that state. Simply learning how to exist in that state is the first thing you learn. Learning to lean into it without trying to generate sound or touch is part of the process. You kinda have to learn that to be able to explore your mind.

I would say that, within this scenario, death would serve to reduce or eliminate the “need” to crave, to chase, stimulation. Without a body providing non stop sensory signals, the mind that was once tethered to a bundle of perception via a brain would no longer be a slave to that brain. That craving for stimulation is part of why people have trouble with sensory deprivation. It’s why, in a perfect silence, we’ll hear things anyway, that humming or ringing of the ears, nerves, and brain trying to process something that isn’t there.

Our brains expect to “hear” things, so it generates a “ghost” sound akin to a dial tone.

But without the brain, maybe we would be free of that, and exist in a state where thought is the only thing that is.

https://en.m.wikipedia.org/wiki/Floating_man some related thinking, particularly the parts about knowledge by presence.

One would go crazy. This would be an extreme verion on solitary confinement.

To the question. One may learn lots if untrue things.

Memory works partly through the same mental routes as new sensory stimuli. For instance, if you think about a sunset, your brain uses some of the same pathways that would be used if you were looking at an actual sunset. So, if you can recall things you’ve sensed before, you could figure out new things about them.

And then there’s a-priori things like math. If you already have learned a notion of logical consistency, and if you have a good enough memory, then you could (for instance) work out new theorems or geometric constructions.

Yes, in rehashing I think you can come up with new ideas that never occurred to you.

Sort of. I guess if you had all the time in the world to reflect on your memories, you might come to some realizations that you never had before, but you’d never have any way to confirm them.

For example, say you think about some of the things your best friend had done over the years, and you think that maybe they were just taking advantage of you, and wasn’t really your friend. You “learned” something, but there’s a good chance that’s not true at all, and simply the result of having all the time in the world to over analyse your memories.

There’s that idea that your thoughts are determined by quantum particles interacting with your brain. So if you still have a body, even without your senses, you might still be able to just pull information out of the aether through this process.

Depends on what “You” is.

If:

You = Universe (as in Pantheism), then yes, you learn from yourself, you are the universe after all.

Absolutely. If your consciousness is present, you can learn things about your consciousness. How to access different states of consciousness, realizations about the nature of consciousness, whatever can be learned through meditation.

And, aside from that, honestly, I come to a lot of my knowledge/realizations about particularly STEM kind of subjects long after having had the external stimuli that is educational study. I didn’t intuitively “get” logarithms until long after I finished college, and I don’t think for any reason related to any external stimulus at the time. I was certain my realizations were “correct” without external verification. I had everything in my mind already necessary to confirm them. And when using that knowledge in situations that did involve external stimulus, the realizations bore fruit. (To put the realization into words, it would probably be something like “logarithms are roughly just a measure of how many digits an operand is in a given numerical base.”) I’ve had similar realizations long after the fact about trigonometry.

There’s also the possibility of recalling things you’d forgotten.

Several people here have raised the objection that without external confirmation, it can’t be called “knowledge” as there’s no way of confirming it. But I’d counter that there’s not really a difference. There are ways to confirm knowledge without external verification (“thought experiments”, for instance). And there are limits on what can be verified and what can’t be verified even with interaction with an “objective external world.” (Even with an external world, how can you be sure it’s external and not something you’re making up as you go – a believe called “solipsism”? Short answer, you can’t. So can you claim as “knowledge” anything you “confirmed” by interaction with the world you think is “external”? How can you be certain you’re sane enough to be able to trust your confirmations? You can’t, and the fact that you can’t doesn’t hinge on whether you have access to an external world.)

Yes, there are limits to what can be learned from the external world. (For instance, you can’t verify General Relativity is something that’s a thing in “the external physical world” (assuming there’s only one, that is!) without experiments in the external physical world which you hypothesize may be well described by General Relativity. But if you came up with General Relativity on your own without external stimulus, you could learn many of its consequences should it prove true. And “if this then that” conclusions can definitely qualify as “knowledge” even if you don’t know if the “this” is true or not, I’d say. ) There are also limits to what can be learned from interacting with the external world. (Like realizations about your own psyche.) I think you’d have to pretty much ignore the “hard problem of consciousness” entirely just because it’s inconvenient to conclude that you couldn’t learn things without external stimulus.

No