Everything is a belief. Even facts. Facts are representatives of reality, rather than reality itself. The universe itself may be an illusion and it’s laws only applicable to our experience of them. What exactly the universe is, and what exactly reality is, is not known. All we know is our interpretation of it.
Fact: I’m writing this right now. Actually, I, whoever I am, is experiencing the act of writing. Which is itself an indeterminate thing. And “right now” is a subjective term, because time is relative, as Einstein pointed out in his theory. But there’s one fact that can’t be disputed: something exists. Something is being experienced.
What I’m experiencing in this moment seems very real. Even my experience of self. For that reason I know that experience itself exists. Even if it turns out that this is all an illusion, something was still experienced.
Our experience of reality is more than just our five senses. If a child was born without those senses it wouldn’t be able to experience “physical” reality, but it wouldn’t be brain dead. It would still experience something. There’s something more intuitive. Something “spiritual.” One could argue that it’s only neurons creating that inner experience, but what are neurons? At the quantum level, what are they? We don’t know.
We’re not able to define reality, we can only define our experience of it. We can’t define it, because we can’t detach ourselves from it. We’re part of it. We’re entangle with it. If we were to somehow detach ourselves from it, who would that “we” be? The nature of reality isn’t something that will ever be defined by us. Our mind is not able to comprehend it, let alone able to put it into words.