In his doctoral dissertation, Bange re-assesses the theory of Cross and Freedman that vowel-letters appeared first in Aramaic in final position due to the dropping of final short vowels leading to the change of the 1cs suffix from –iya to –iy to –î. Bange first challenges the assumption that in a consonantal orthography every diphthong must be indicated by its consonantal element. He argues that Northwest Semitic orthography moved through three stages. First was the fully consonantal stage in which the semi-vowels yod and waw were only written when they had full consonantal value (defined as being followed by a vowel, ie they form a proper CV syllable). The second stage is semi-consonantal orthography (10th – 7th centuries). In this stage the spoken dialects diphthongized a certain number of vowels and aleph, he, yod, and waw became semi-consonants, used often to indicate diphthongs after accented vowels in open syllables. The aleph functions as a glottal stop while the he is a glottal off-glide, the waw is a labial off-glide, and the yod is a palatal off-glide. True vowel-letters do not appear until 6th century as the results of historical spellings when the function of these letters as off-glides was lost. Certain consonants were associated with certain vowels based on analogy. Thus in Aramaic aleph, which was used ubiquitously for the emphatic state, became associated with /a/ while in Hebrew it is he that is primarily associated with /a/. This also suggests that Hebrew did not borrow vowel-letters from Aramaic, but that they developed independently as the same structural forces were at work in each language.