I don't believe it's possible to make a clear distinction between "naturally" and "by directed effort" in the case of language. The degree to which a person is

I don't believe it's possible to make a clear distinction between "naturally" and "by directed effort" in the case of language. The degree to which a person is conscious of the change they are making might be a theoretical criterion, but it would usually be impossible to apply it in practice as in most cases we don't know who the person was, let alone what their mental state was at the time. Even if we know who made a change and they are still living they usually wouldn't be able to tell us reliably what they were thinking. There are plenty of individual English words whose spellings were deliberately changed by some person for one reason or another. Perhaps the only major change affecting a large number of words promulgated by a single person was Noah Webster's reform of American English that created most of the differences between American English and British English. There's a book called Does spelling matter? which has a lot of information about English spelling and historical reform proposals (though the book is perhaps not entirely reliable: there are some weird non-sequiturs in it that made me suspicious).