Put another way, using our current knowledge of physics and chemistry, we can, on a high level anyway, account for every item in the cause and effect chain from the photons hitting the retina to the arm that a person raises to shade his eyes. There is no room to insert anything into that causal chain let alone something so massively influential that it causes all the body actions that we consider driven by conscious choice. Thus whatever is going on must be made from very ordinary matter.

It's this very fact that makes it such a fun puzzle to look at, very ordinary mater maybe doing something (causing consciousness) that is wildly unexpected.