 The reason that Peirce believes these ten elements will yield sixty-six classes is clear enough, the same combinatorial considerations given for the interim typology (outlined above in 3.4) apply here. However, the precise manner and order in which these elements interact will determine what the sixty-six classes of signs will look like in the final typology. Unfortunately, these ten divisions and their classes represent a baffling array of under-explained terminology, and there is little to indicate precisely how we should set about the task of combining them. Even though we may be confident on the number of signs in the final typology, other details are sketchy and underdeveloped, and there still exists no fully satisfactory account of the sixty-six classes. As Nathan Houser points out, “a sound and detailed extension of Peirce’s analysis of signs to his full set of ten divisions and sixty-six classes is perhaps the most pressing problem for Peircian semiotics”. (Houser 1992, 502).