• Do we know that anything exists unperceived?

    No.

    The boiling soup is in front of you. You close your eyes, and it vanishes. Has it ceased to exist? You still hear it boiling. Does it still exist? Maybe something else is making that noise. But you can smell it? Maybe something else is producing that smell?

    You're deaf and blind. You have no sense of smell. Does the soup still exist? You reach out and touch the boiling soup. Ouch. What if you have no sense of touch? Or if you can't reach the soup? Does it exist?

    Well, at this point you're nothing but consciousness. Do you exist? Descartes says you do because you are conscious of yourself. But what is it that you are conscious of? Only your own consciousness.

    Your consciousness is axiomatic. You can't contemplate your own consciousness without reference to it. So you know that for sure. It's the only sure thing.

    But that ain't too satisfying, is it?

    Does existence exist? Well, that's axiomatic, too. How can you contemplate existence without existing?

    If you exist--and you do--do you exist alone? Perhaps.

    That's all very cute, and very obvious. But what about that boiling soup? You regain your senses and the soup reappears in all its smelly, noisy glory. You perceive it again. But what does that mean? Maybe your view of the soup is totally subjective and it doesn't exist for the other perceiving consciousness sitting at the table opposite you. Maybe you're imagining the soup. You go to serve it to the other but they can't receive it since for them it doesn't exist. Is it getting a little nutty?

    At some point, everything is axiomatic since you can't interact with it unless you reference it in the interaction. And others can't interact with it unless they too perceive it in about the same way you do. You could say that objectivity--that entities exist independent of your consciousness--is the degree to which subjectivity doesn't obtain; the degree to which axiomatic-ness is common.

    You're living in the Matrix. And that matrix is called reality. Yes, the boiling soup exists.