What is a language?

["61510::GILSON" <cbmvax!uunet!CFE1.NRL.NAVY.MIL!pucc.PRINCETON.EDU!gilson!61510.decnet>]

For those of you on both the lojban list and the conlang list,
I apologize for the fact that you will get one of these via
each pathway. I think that this is relevant to both groups,
even if more to conlang than to lojban-list, so I am sending it
to both groups; since I know that there is a lot of overlap but
not 100%, this seems to be necessary.

The question comes up as to what is a "real language": Is Esperanto,
or lojban, or Cornish? I feel that nothing is gained by unduly
restricting the list of "real languages." A language with only one
speaker is still a language, if he/she uses it (say, in a diary,
which enables him to communicate with him/herself at a later time).
Certainly Intal, say, qualifies as a language, since Erich Weferling
wrote the Intal grammar in Intal, and Ivan Derzhansky and I read it
in Intal, and not in the German that certainly was Weferling's thought
medium.

I think that we should certainly accept as a language anything other
than a direct letter-for-letter or word-for-word coding of another
language. Morse-coded English is not a different language from English,
because it is isomorphic to written English. American Sign Language
is certainly a language; it is NOT isomorphic to written English.
Intal may follow German in distinguishing two meanings of English "know"
but it is not coded German; it has a well-defined word order different
from German.

We might rather more profitably accept as a language anything with any
pretension to being one, and use qualifiers to distinguish such as:

a living language = any language with at least one speaker;
an active communications language = any language with at least two
                                    speakers, who use it as a means
                                    of communication;
a primary language = any language that has at least one speaker who
                     habitually thinks in it;
a first language = any language which is the initial exposure to
                   language of any individual.

I do not claim that these are all the possibilities. We might want to
distinguish Lojban (which has a few speakers, but none fluent, if I
understand Bob LeChevalier's level of ability properly) from Esperanto
(which by now does have some fluent speakers), for example.