Reality commonsense ego

:When a being is conceived he is nothing. No ego no self just a set of cells arranged in a unique way. This will have the hereditary characteristics. After convincing the being will get inputs from the environment through it's senses this information will be arranged in its brain.some will be deleted some will be rearranged.This information and what it inherited will make the ego of a person. Reality according to the person is this mix of data. When the person thinks this is my arm it is the data arranged in his brain. Language is the tool that connects commonsense to you. When I say this is my hand everyone else understands it. If I am a lunatic and my brain if different from others. I see my head not on my neck but on my hand. This is my head showing my hand. Everyone else will see the statement as absurd. So the absurdity arose not because the position of my head but because the differences in the brains. Suppose a deformed person has his head in his arm then the absurd statement becomes true! Reality is an illusion created in the brain.the beautiful mountain or sunset we see are really created in our brain. The mountain may actually exist in some form but our perception makes the beautiful appearance we see. This will be true for everything in the universe.
Music is more easier to understand. A set of frequencies gives a harmony to human ear. Its because of the human brain. We can extrapolate it to our physical world.
universe
Suppose a cow grazing grass sees a beautiful mountain in twilight. Can it enjoy the beauty? It will see the mountain in a very different perspective than a human. A primitive human looking at the night sky will have a very different perspective of the universe than a modern human. It shows that reality is different though there is not much difference in the structure of the human brain between then and now. Only difference is accumulated knowledge.