What linguistics is not:

Asked what my job is, I always just say that I am an English teacher. But I am also a linguist, a fact that I often keep secret especially in front of those who I've just met because of the difficulty of explaining what an average linguist is up to. Different linguists do different jobs, and it often happens that those who believe themselves to be linguists are not so regarded by others. Indeed, pinning down linguists' jobs is not a little tricky. But this does not imply that linguistics is a recondite discipline that is beyond ordinary people's ken. So, as there seem to be a lot of confusions or misconceptions among laypeople about what it is the duty of the linguist to do, it might not be so superfluous here to provide a general and neutral adumbration thereof, or at least of what is not her duty to do---though I must hasten to add I myself am not so knowledgeable as to this occupation as to be equal to the task. The following sketch, for the validity of which I cannot vouch at all, is intended for laypeople, so it is written in as easy a manner as possible.

First of all, if you think that a linguist is a person who can speak several languages fluently, you should drop the idea immediately. Although most linguists can speak at least more than one language, theoretically one can do linguistics without knowing about any languages other than one's own. One of the culprits for this misunderstanding is, I think, the fact that the English word "linguist" has several meanings, one of which is, unfortunately, "a person with a good command of foreign languages." But you should keep a line of demarcation between this figurative meaning of "linguist" and what a professional linguist means. The purpose of the linguist is to clarify scientifically what a specific language or human language in general is, not to become proficient in many languages, though this kind of proficiency ultimately proves to be of use to her.

Second, if you believe that the duty of the linguist is to show people in general what kind of rules they should follow if they are to speak correctly, it seems that you do not know anything about linguistics today. As early as 1909, a Danish linguist named Otto Jespersen, whose influence on this field cannot be overstated, maintained that the purpose of the grammarian is not to prescribe what grammatical rules "should be" but to describe what grammatical rules "are." Yes, there are language mavens and grammar snobs, who are persnickety about what they perceive to be correct usage and show no restraint whatsoever in excoriating those who they think commit the error of flouting their sacred rules. Sometimes, these fanatics may subsume themselves under the category of "linguist." But if they are linguists, I am a Martian. A true linguist approaches verbal phenomena as a botanist approaches herbal, or a zoologist animal, phenomena. She does not dictate which expressions are correct and which not. Every expression, as long as it is sufficiently widespread, is a legitimate object of her study, because it is a legitimate member of the linguistic world no less than a species of animal is of the animal kingdom. True, language mavens may suggest that you stop using such expressions as "I could care less" and "The reason is because he is a nerd." But from a professional linguist's point of view, it does not make sense to judge whether these expressions are "correct"; what piques her interest is why they have emerged.

Finally, if you suspect that the job of the linguist is to provide a(n) historical explanation of a word or a construction, well, you are not wide of the mark but still not to the point. Those who do this kind of work are usually called "etymologists" or "lexicographers" and now distinguished from linguists. I say now because there used to be a time when the job of the linguist was to explain language phenomena on historical principles. In those days, it was generally believed that the only way to explain why certain words or constructions existed was to appeal to the history of the language. But an iconoclastic Swiss linguist called Ferdinand de Saussure challenged this then impregnably predominant idea on the grounds that it should be possible to study any historical phase of a language independently of all the others, to draw a line between synchronic and diachronic aspects of human language, a distinction that is still influential in the field of theoretical linguistics, though some attempts have been made to revise it. So the job of linguist today is not to provide an etymological explanation.

"Then, what is the linguist doing? You say that she is studying scientifically what language is. But this is too vague. What I want to know is specifically what kind of activity she is engaged in." You might complain. Sorry. But I have no intention of equivocating. The vexed/vexing problem with the definition of linguistics is that what it means to scientifically study language differs from one person to another. Some say that the word "scientific" means "in a manner as rigorous as natural science", while others say that geistwissenshaft (human science) is completely different from natural science, with myriad less extreme interpretations of "scientific" in between. So beyond this, it's up to the individual what is within the proper realm of the linguist to do. Ah? My stance? I believe that I am standing in the middle of the spectrum, equidistant from the two extreme poles, since I am an advocate of the golden mean. But perhaps that's just because they are equi-valent (gleichgultig) for me.