Everything is not a fox

From The Maze Where Realities Converge - the psychedelic encyclopedia of reality from The Ultimate Comment

A sudden revelation which dictates that everything is not, in fact, a fox, as we may have once believed. It more leads to the question is everything anything in particular? Is it a universe? Is it just everything? Does everything even exist or is it just a concept we invent as humans to try and encompass our sensory world, when in fact there could be no limit with which to define "ok NOW we've listed everything"?

Also, if everything is not a fox, what things ARE a fox?