Today's class was looking at the legitimacy of varieties of English, among other things.
Whenever I do this class, the students looking at the different language/varietal examples always decide if something is legitimate based on two aspects: intelligibility and familiarity. Whether or not it is "pure" - whatever that means - doesn't seem to have a bearing. For example, they always decide that Old English (Anglo-Saxon) is not legitimate, as it does not fit the two criteria of intelligibility and familiarity.
I always feel rather good about the decision to base legitimacy on intelligibility; if a speaker of English is clearly spoken, or if written language expresses ideas clearly, then that's the important thing as far as I'm concerned, although this may not address the issues raised in the term "legitimate". The familiarity criterion is something of a problem, however.
In terms of whether a variety of English is accepted as a New Variety (NVE), of course it has to be shown that the code has regular, observable patterns which are used by a homogeneous group of people in a number of different settings. Having the variety as an L1 is also often given as an important criterion. However, this does not mean that the NVE is necessarily intelligible, and it is not always the case that it is going to be very familiar to all other speakers of English.
Here is the conflict - if you like - between the description and acceptance of NVEs / world Englishes and approaches such as the Lingua Franca Core; just because something is an established variety it does not mean it is intelligible (many accents of British English are not, for example) but, in order for people across the world to communicate in English, if it is to be THE international language, there has to be enough commonality in the code for people to be able to understand each other and - at least to some extent - for it not to be too unfamiliar.
So what we're talking about here is people being diglossic, i.e., having access to and being able to use both their own variety of English and to be able to switch to a code which is intelligible to as many (other) speakers of English as possible. This situation already exists in some countries such as Singapore, which has Standard Singapore English and also the more localised Singlish, often vilified as basilectal. This is a bit of a simplistic description but it will do for now.
Is this too much to ask? Well, I don't think so, but I'm fortunate enough to speak a variety or ideolect which, I'm told by a lot of people, is very clear - and I haven't got RP (which, in its most extreme form, is not always clear!). Where other native speakers of Old Varieties of English (OVEs) are concerned, this may be a hard sell; if you've been speaking English all your life and then someone tells you you'll need to change it so someone "foreign" can understand you, rather than the other way around, my sense is that there might well be resistance to this.
English, just as any language, grows and changes. What speakers of OVEs who are not intelligible have got to realise is that, to keep up, their English will need to grow and change, too. I really wouldn't want us to get left behind. We're fortunate enough as it is that English has emerged as the international lingua franca in the way it has; resting on our laurels is really not an option.