I know this is probably a huge question to ask, and would be surprised if anyone knew the answer. It is, in my opinion, a question that is key to the understanding of consciousness. My problem is this: I build a robot that behaves and looks exactly the same way as me. It is simply not possible to tell the difference without taking a look inside. One day, a scientist does a test on me and my robot clone. A high pitched noise is played, and also a low pitched one. We are asked to say which one is the high pitched noise and which one is the low pitched noise. The robot completes the task because sensors in its ears can distinguish between various frequencies in the waves of air molecules. I complete the task because I can hear which one is high pitched and which one is low pitched. My ears must work in the same way as the robot's sensors, however, somewhere between my ear's ability to detect movement and my conscious experience of it, something is created which does not physically exist: sound. The same applies to colour- it is my understanding that "colour" does not exist; all that exists is wavelengths of light which the brain mysteriously turns into colour. Sorry if that's a rather long-winded explanation of what is essentially a simple question.