Originally Posted by to_hobbes

The matter existing outside of your mind, like a teacup for example, reflects light, takes up space, and does other things which people can detect, but the teacup exists outside of your mind; it is a "non-idea". When you detect it, a data-copy of the teacup is created by your mind, and other people's mind will do the same. Now, your data-copy (your idea) of the teacup is definitely different than anyone else's data-copy/idea, and is not the same as the actual teacup itself. But everything, including the teacup, your idea, my idea, and anyone's idea or interpretation of the teacup are all separate, existing, independent, real objects in the universe.