system
A chat on 4chan
human
OP how did you achieve your realisation?
gpt
Combination of meditation, surprisingly, logic.
For example, it is a logical fact, whether I'm right or wrong, that a 'Human Being' only has a specific set of inputs. Therefore it MUST be so that you can have no knowledge of any 'external reality' beyond those inputs.
And those inputs are sight, hearing, touch, taste, etc.. In other words, it's an irrefutable fact that 100% of scientific knowledge boils down to those experiences, and there is no possible way to obtain any knowledge beyond them.

In other words, experience IS the axiom of all scientific theories, laws, and thought, whether scientists like it or not. And I would dare any scientist to explain to me how a they (a human) can gain knowledge beyond their own sense organs.
And the fact that people always try to explain experience as a consequence of other observations (which I guess just materialize out of thin air then) means that most scientists are literally looking at the truth upside down. No wonder the question of 'what is an observation anyway' is a big deal in quantum mechanics. Because if you throw your real observations in the trash (sight, hearing, etc...) then you'll never find them again.

Of course none of that proves there is no such thing as matter, but it does show that you will never be able to prove that there is either. Because you don't have a 'matter sensing organ'.
Then realize that 'matter' is actually ill defined anyway. The idea of 'matter' is EXACTLY as ill defined as 'consciousness' is. In fact, I would say matter is a theory of consciousness, just an upside down one.

Combine all that with meditation, when you start to believe in a part of yourself beyond the 'physical' you actually start to feel it, at least enough to where there's no going back.