 While the philosophy of perception has been the area where the conceptual/nonconceptual distinction has been most discussed, the theory of nonconceptual content has been fruitfully employed in other areas of philosophy. A case in point is the study of self-consciousness (see the entry on  self-consciousness).  In 1998 two books independently developed theories of nonconceptual self-consciousness (Hurley 1998 and Bermúdez 1998). Bermúdez and Hurley both emphasized prelinguistic forms of self-consciousness, arguing that linguistic self-reference and associated modes of conceptual self-consciousness both emerge from, and need to understood in terms of, much more primitive forms of self-specifying information. For Bermúdez these include: