The cartoon characters "The Numskulls" appeared in The Beano when I was a kid. The idea was that the man in our world was filled with miniature men - who specialised in one sense or function for the life-size figure. Thus, the Numskull in the stomach was forever shovelling fuel into a furnace, the one in the "Brain Dept" was getting print-outs from a contemporary computer and - my favourite - the one in the "Eye Dept" wore glasses and looked through a telescope in the eye.
The obvious problem with the Numskulls is that if the senses are perceived by a number of miniature characters inside, then how does each of those mini-men perceive? If you say they "just sense it" - then why don't you say that of the life-size figure. But if you say that there are even smaller men inside their heads, behind their eyes, etc. then you start upon an infinite regress, because the question will be how do each of those mini-mini-men perceive their sense-data? And so on.
I sort of knew this as a kid. I couldn't express it, but there was this niggling dissatisfaction with the idea of them - it just didn't feel right. I wanted to understand what really happens "inside" humans. I still do.