The word metaphysics derives from the Greek meta ta physika (literally, "after the things of nature"), an expression used by Hellenistic and later commentators to refer to Aristotle's untitled group of texts that we still call the Metaphysics. Aristotle himself called the subject of these texts first philosophy, theology, or sometimes wisdom; the phrase ta meta ta physika biblia ("the books after the books on nature") is not used by Aristotle himself and was apparently introduced by the editors (traditionally by Andronicus of Rhodes in the first century BCE) who classified and cataloged his works. Later, classical and medieval philosophers took this title to mean that the subjects discussed in the Metaphysics came "after the things of nature" because they were further removed from sense perception and, therefore, more difficult to understand; they used Aristotle's frequent contrast of things "prior and better known to...