that is linguistic fact as well as theory. Dialects and languages are classified by what is mutually understood in a high percentage of cases, but not 100%. So this entire exercise is interesting and true for over 98% of its content, but not 100% true. The only thing that is 100% true is the generalization that English spelling and pronunciation are highly irregular. And they will remain that way until homonyms and homophones are clearly distinguished and both old and borrowed