There is a big difference between internal and external objects. Internal ones do not have a mass, external ones do. (Actually dream objects have a mass, but it is so miniscule it can be disregarded) We ‘never’ perceive Reality ; we perceive our interpretations of that reality. Let’s take a look at the sense of sight; all other senses operate the same way. Light bounces off some “real” objects, enters our eyes, hits conns and rods, becomes chemical reaction, affects optical nerve where it is converted into electromagnetic impulse, travels to the brain WHERE the images of the objects are created. (This is what science investigates) So all of this, which you are perceiving with your 5 senses is supposedly in your brain. But our brain is also an image created by the electro -magnetic impulse traveling to this same brain (?!), this includes the sun whose light reflection we perceived originally. Question arises, can we perceive reality with our minds directly, and not just through our senses? Some believe they see dream objects with their dream eyes……The existence is of the mental nature… But this does not make ‘physical ‘ world non-existent. It is as real as anything will ever be, because the existence of this universe is upheld by infinite number of living beings…