English grammar is so complex and confusing for the one very simple reason that its rules and terminology are based on Latin—a language with which it has precious little in common. In Latin, to take one example, it is not possible to split an infinitive. So in English, the early authorities decided, it should not be possible to split an infinitive either. But there is no reason why we shouldn't, any more than we should forsake instant coffee and air travel because they weren't available to the Romans. Making English grammar conform to Latin rules is like asking people to play baseball using the rules of football. It is a patent absurdity. But once this insane notion became established, grammarians found themselves having to draw up ever more complicated and circular arguments to accommodate the inconsistencies.