"PHILOSOPHICALLY SPEAKING...":

Those interested in the philosophy of language may enjoy this provocatively titled article "Do Languages Exist?" from Philosophy Now (UK):

"Languages seem an important feature of our lives. The languages we speak determine who we can communicate with, where we can work, and what we can read or listen to. Languages are also political. For instance, recent years have seen laws requiring migrants to the UK to learn English. An apparent decline in numbers of Welsh speakers led to calls for government money to be spent on Welsh language promotion. Kiev saw rioting in 2012 in response to moves to allow the Russian language, rather than Ukrainian, to be used in public institutions. Given the powerful role that languages play, it is perhaps surprising that some thinkers claim that such languages do not actually exist. ...

"[A]lthough at first sight it seems simple to identify different languages as ‘English’, ‘Welsh’, and so on, on closer examination, our way of dividing linguistic phenomena into so-called ‘languages’ seems arbitrary. To use [American linguist Noam] Chomsky’s example in Knowledge of Language (1986), Dutch and German are traditionally treated as separate languages. However, some German dialects are closer to Dutch than to other German dialects, with which they are not mutually intelligible. Thus, our standard way of dividing different forms of speech into ‘Dutch’ or ‘German’ does not capture any real aspect of the world, but arbitrarily groups together linguistic phenomena. ... [S]ome folks believe that the phenomenon of human language is best understood not as a series of languages like English or Welsh, but as a series of idiolects. An idiolect is the language of one individual. A description of one person’s idiolect includes all the vocabulary and grammatical features of that individual’s personal way of speaking (or writing). Their idiolect is an independent, self-contained system. ... This view holds that individuals’ idiolects, as opposed to mass languages like English, are the only form of language that exists. ... Of course, there are similarities between idiolects. For instance, most people living in Germany use idiolects similar to those of other German residents. However, there is no such thing as ‘the German language’; only overlapping independent idiolects. ...

"One alternative to the idiolectal view sees a language as a social convention. ... Take the convention of driving on the left-hand side of the road. This convention, which existed long before it was written into law, arose for obvious practical purposes, such as preventing crashes. [The late Princeton philosopher David] Lewis notes that this convention only functions because all British, Australian, etc drivers recognise that it is in force, follow it, and expect and hope that others follow it too. Of course, they could equally well have followed the French and American convention of driving on the right to achieve the same ends. However, once a convention is in place, it often remains that way for as long as it is generally useful. A language, Lewis argues, is established and maintained in a similar way. Take the English expression “It’s raining.” The convention that we utter “It’s raining” only when we believe that it is raining exists for useful communicative purposes. Of course, for the convention on this use of sounds to work, we all have to recognise that it is in force, follow it, and expect and hope that others follow it too. ... On this ‘public language’ view, English, Welsh, and other languages, can be seen as complex systems of conventions. The conventions arise and endure because they solve coordination problems between individuals in a society. Thus, a language is essentially interpersonal. In contrast to the idiolectal view, a language cannot be regarded as a system confined to one individual."
philosophynow.org/issues/100/Do_Languages_Exist