For instance, I believe in a historical exodus. But I think his theory is bunk. You see, there are three phonemes (sounds) in the Hebrew language during the first millennium BC that don't have their own letter. It's all about the history of languages and stuff. I can't do a better job of explaining it than Eric Reymond does in ch. 2 of his forthcoming book Intermediate Biblical Hebrew Grammar: A Student's Guide to Phonology and Morphology:
The inventory of Classical Biblical Hebrew phonemes listed above [in a chart] is three greater than the number of graphic letters used to represent these sounds. This resulted in some letters representing more than one phoneme. Specifically, three letters were used to represent two phonemes each. The khet represented the phonemes /ḥ/ (IPA [ħ]) and /ḫ/ (IPA [x]). The ayin represented /ʿ/ (IPA [ʕ]) and /ġ/ (IPA [ɣ]). The sin/shin letter represented /ś/ (IPA [ɬ]) and /š/ (IPA [ʃ]). (Recall that the dot that distinguishes sin from shin is a medieval invention.) The existence of the phonemes /ḫ/, /ġ/, and /ś/ is thought to have existed in the Late Bronze Age Canaanite as implied by names and words in the El Amarna texts as compared to Egyptian transcriptions.[footnote:Daniel Sivan, Grammatical Analysis and Glossary of the Northwest Semitic Vocables in Akkadian Texts of the 15th–13th C.B.C. from Canaan and Syria, AOAT 214 (Kevelaer: Butzon and Bercker; Neukirchen-Vluyn: Neukirchener Verlag, 1984), 50–52.]So, you see, in order for Petrovich's idea to be correct, he would have to posit that the 3 double-duty letters merged about 1000 years before they did and then divided again about 100–200 years later only to merge again in the first century (or thereabouts) BC. Sorry. Not buying it.