The brain. It is an illusion of the brain.

A set of neurons gets some input and that feeds into another set of neurons that has to make all the information from many sources coherent. Those neurons label the input firing pattens as qualia and then act as if they were experiencing the world rather than just signal processing, and so ‘experience’ is not real in any metaphysical sense.

I’m not 100% sure I believe that theory, but I do find it highly plausible.

> The notion of an illusion requires an observer

In this debate, "consciousness" is an ineffable quality that goes beyond perception. Illusions only require perceptions for a self, not consciousness.

The system reacting to itself, but thinking that it is looking at a separate system.