It is all in your head.

In a sense, this is not a theory at all.

See, when you see things, when you hear, feel, or at all experience anything, that is all information inside your brain.
When you see things outside of yourself, like your shirt, that object is actually in your head. Nothing is at all outside of your brain. Infact, everything is even made up by the brain! Well, in matter of experiencing things.
So, we are all pretty blind and all when you think about it. We don't 'see' through our eyes, we see stuff that is being recepted in our head. same thing with hearing, with feeling, smelling, tasting.

We don't even know what everything is outside of what we perceive it as in our heads. Color, sound, whatever. Wwe don't even know what color our skin is outside of our eyes.

Wierd.

Nice thought. I'm afraid to touch anything now. It's all strange to me. Cool.

Yep, I've never thought about it in such blunt terms, but that's what it is.

when you think about it, the universe consists of two things--space and matter. and these, outside of our heads, are nothing more than two conflicting opposites, which is the basis of all existence, really. the universe in our heads consists of a much greater array of things than this.

What about forces of hot and cold?

heat is energy, which according to einstein, is the same thing as matter--interchangeable. and cold is not anything--it is simply a lack of heat.

I get what you are saying.

What if that is all it was too?
If every single thing that you ever saw was just energy. Matter, what you touch, what if it had nothing to do with body, but your energy coming in contact with the objects's energy is what slows you down, stops you, whatever.

yeah, im no physicist, but i think that's pretty much it in a nutshell.

I think that your refering to the problem of perception here , but in a more general sense. this is a valid theory tied in with knowledge. How ever , you seem to believe that you know things in your head , even though your dismising an outside reality. which if you deduce it back doesnt follow logically. However , as far as knowing things is concerd , have you ever wondered what properties knowledge should have? It was once thought obvious that a true justified belief was the basis for knowledge , but if you cant think of any reason as to why its not, then check out gettiers counter examples. although a bit more specific than 'everything is in your head' , you still might find it interesting if you had the general concept of what do we actually know.