Certainly people differ from time to time, but I think people have biases towards such bottoming out of reality. If you bottom out with people you are more likely to see some sort of God as the prime mover. The rock person may be more likely to imagine the first rock. Descartes believed in God as did most intellectuals of his day. He might have been attracted to Tegmark’s universe as mathematical reality. Krauss describes a ‘Universe from Nothing’, which may seem an oxymoron, but so are all of the bottoms.
It seems to me that there is something underneath both ontology and epistemology. I lack any organized ideas on its nature except that it has to do with how our brain helps us survive. I may want to limit this groping to less than total brain function. Lets limit it to how the brain learns about the world and what it learns to help us to survive better. We might consider how the brain holds a model of the world. But this is already too much as reflexes that help us walk are actually about the world. I would like to cleave off reflexes, but that may be an unnatural cleavage.
On the first page of Everetts “Many Worlds” paper he speculates on the simplest example of observer and observed. He postulates to elementary interacting particles and the suffices for his purposes. We might split off world knowledge that is in our DNA.
What are the ramifications of there being a model here of something there?