Historically, one can distinguish different world-views on reality:
1. Physical realism. Only the physical world exists, so it is observing itself.
2. Solipsism. Only the mind exists, so the physical world is like a dream created by the mind.
3. Dualism. The physical world exists, but is also observed by another higher world beyond it.
one could go on ...but let us stop there
Self as illusion of th brain