A modern version of Descartes’ problem is a thought experiment called the ‘brain in a vat’. Hilary Putnam tells us to visualize our mind a human being that “has been subjected to an operation by an evil scientist. The person’s brain…has been removed from the body and placed in a vat of nutrients which keeps the brain alive.” The person’s nerve endings are connected to a computer that allows that person to have the illusion that everything is normal. The illusion lets them believe that there are “people, objects, the sky, etc.; but really, all the person…is experiencing is the result of electronic impulses travelling from the computer to the nerve endings.” If a person was to even raise his hand, the computer is capable of letting him “see”