Something exists outside of my body. The way I interpret this something exists only inside my head and no in the outside world. Therefore my world exists only in my head but a world outside my head influences the world inside my head and this is what each of us call "reality".
There is only one world, one reality, and you're a part of it. What's inside is outside, and what's outside is inside. (John Lennon said that.) There aren't two worlds, inside and out, there's only one --and from your perspective, you're it. And so am I from my perspective.
When you see a cloud in the sky, that cloud that you see is knowledge in your mind. It got there through senses, but by the time you "see" it it's already "inside," drawn from immediate memory. All the world that you
know --all the outside --is knowledge. That cloud that is "outside" is inside you.
You turn to me and say, "Do you see that cloud?" I'm busy, so I don't look up. "No, tell me about it." You describe the cloud to me, and I can picture it in my mind. Then I look up and see the cloud, and can even point to it and say, "That's the one you meant, eh?" and get a nod. But it's my inside that I'm pointing to.
How can it be that we both see the
same inside while being two
separate insides? Some people say that it proves the outside, beyond a shadow of a doubt... but that doesn't really explain anything, since it's still inside. Some say that, rather, it indicates a flaw in the whole "inside-outside" way of thinking. It proves no inside different from an outside. All the world is inside-outside, or to word it better, there is
no difference between inside and outside --none at all. The split we give them is arbitrary, given to maintain the sense of "self" that distinguishes "me" from the world.
Reality is "me, in the world."