They call is doubt experiment. It is a mind experiment. Descartes found that he could doubt material things. So he took it to the extreme and doubted everything. In the end he was left with his thinking mind, and this thing he could not doubt. He famously expresses, cogito ergo sum. I think, therefore I am.
Mind over matter. Mind as creator. Mind as subject, the other as object. The conclusion is simple. A 5-year old would come to it. But Descartes cheated and gave us the opposite result. He was greedy for scientific products, and we are all greedy with him. We buy into the same faulty logic.
But it doesn't matter. You go back and correct it. Mind over matter. Problem solved.