In English, the preposition you should use may depend on whether the verb controlling it is one of motion or one of repose. For instance, to throw is a verb of motion. In ordinary circumstances, therefore, it cannot take the preposition in because that preposition usually indicates or implies rest or motionlessness.
It is, of course, possible in an idiomatic expression like to “throw in the towel”, meaning to surrender, for instance, in a physical fight. In short, here, that preposition is an essential part of an idiom – as in the expression to throw in the towel, meaning, to surrender, to give up a fight).
For instance, Nairobi is in Kenya. There is no other way. The idea of Nairobi having once upon a time moved into Kenya from Tanzania or Ethiopia just does not arise. Hence the question: what does a conscientious subeditor do whenever he or she finds himself or herself in a situation of motion in which the preposition in is, nevertheless, indispensable?
The answer: he or she will use the word into, namely, a form of that very same preposition in which now indicates motion. In this context, then, you do not “move in a jail” (except on the floor to turn your body this and that way inside the filthy and lice-ridden thingummy that serves as your blanket).
No, what you do from the courtroom is you move into jail. I know it because – thanks to my activities as a reporter and commentator – I have often found myself on the wrong side of those who implement the law, not only in my country but also in both Tanzania and Uganda.
It is the powers-that-be who throw you into that appalling place of confinement. This is why the headline “Outrage as doctors are thrown in jail” (splashed across page 4 of The Standard of February 14) is unacceptable in a newspaper that claims that English is its language of work.
Why not? Because in is a preposition of rest and motionlessness. You cannot use it for a situation of motion. You eat in a restaurant; lie in a bed; learn in a classroom, live in a country; study in a library, and so on.
Its counterpart when you are in motion is into. For instance, in order to vote, you have to go into the polling kiosk and those of you who are religious regularly go into a church, a pagoda, a synagogue or a mosque to beseech your deity to favour you with a “blessing”.
However, quite frequently, even across an extremely busy city street, the grammarian of English may accost you to remind you of the “exception that proves the rules”, namely, that, in English, you can also simply enter a temple without any kind of preposition.
In one of his laugh-a-minute pieces, Mark Twain, the American fun merchant, cracks that, although English has more grammar rules than any other human language, there are more exceptions to than there are instances of every one of those English grammar rules.