The second part of this essay used the hypothetical example of a community who said “apple” to mean what we call an “orange”.
Let’s take this a little further. Let’s imagine that our apples-are-oranges speakers use the word in this way because someone, let’s call him Bertie, once got the two fruits confused. This sort of thing happens (the Russian word for elephant is derived from a Turkic word for lion). Now, Bertie was clearly wrong about something: he thought that the word “apple” referred to oranges, and this was an error. However, this error led him to use the word “apple” to refer to oranges, so this became true of his idiolect; it was true, therefore, of one speaker of English, and thus became a fact about English, albeit a rather trivial one. And since languages can cope with a bit of variation,6 and since we all have a right to call things what we want, Bertie wasn’t doing anything wrong or sinning against English simply by calling oranges apples. But he was doing something wrong in thinking that this is what other English speakers did, or if he did so when attempting to speak Standard English.
Now let’s imagine that Bertie’s community is rather isolated from most English speakers and that oranges and apples are both relatively exotic. This is how he got confused in the first place. And let’s also imagine that, through his prestigious position, or his fecundity, or whatever, the rest of this community adopt Bertie’s usage. This changes things a little, because these speakers are not wrong in quite the same way Bertie was. To be sure, they’re still wrong to think (if they do think so) that they use the word apple in the same was as most other English speakers, or that this is Standard English usage. But that does not mean that they’re confused about what “apple” means, in the way that Bertie was. Words are just arbitrary mappings between meanings and signs, and the form “apple” has no inherent connection with any particular fruit. The connection is conventional, and this community has developed its own convention, which happens to differ from a more common convention. That’s all. Having a different convention, regardless of how it arose, is not in itself wrong.
The purpose of all this has been to demonstrate that to be wrong in one’s use of language depends on several things: what one is trying to achieve, what is expected in the context, what one believes to be the case, and so on. In all these things (and more), it is possible to be wrong.
But, very frequently, when people say that some usage or other is wrong, they appeal to the notion that English is a certain way and that any usage that contradicts that must be wrong. But this notion is confused. English is defined by how English speakers use it, just as dogginess is defined by how dogs behave. A dog might do something untypical (just as an English speaker might do something that that’s not typical of English speakers) but that by itself doesn’t make it a bad dog.
Standard English is different. Its boundaries are a little blurry too, but it is not defined as English has to be, and we can often say straightforwardly that some speaker is speaking non-standard English. And sometimes they shouldn’t be, in which case we can probably say that they’re wrong. But let’s be clear on how they’re wrong; if we’re not clear about that, then we mislead and we encourage a false idea of what language is. It would be good if people understood better what language is, and how it actually works. It is the duty of linguists to help make that clearer.
6^In fact, they can cope with quite a lot of it. One of the other false claims people often make is that when people do something wrong with language, they are harming the language. This is almost always not true.