It is also non-falsifiable since it is impossible to prove or disprove whether ancient people were conscious or not. Or for that matter whether a present-day schizophrenic is conscious or not in the same sense.
Can we even prove whether a modern person is conscious? If so, shouldn't we be able to occasionally encounter such unconscious people, either occurring randomly by natural variation (especially given how recently the breakdown is claimed to have happened), or in people who had very little contact with language (hard but not impossible to come by)?
It’s easy to imagine that somebody raised by apes or otherwise totally isolated from humans would not be conscious, but without teaching them to think consciously how could we ever know?
