It’s an existential problem, in the truest sense of the word: To be or not to be, as poor Hamlet famously mused.
What the Danish prince did not know (and likely didn’t care about too much at the time) is that Japanese ways of “being” make a categorical difference between animate and inanimate objects. The verb that is used to describe the existence of people and other animals is いる (iru), while for all other matter (radishes, ideas, drinking parties) ある (aru) is used.
The two Japanese “be” verbs occur most commonly in combination with the subject particle が, as in 寝室に蚊がいる (Shinshitsu ni ka ga iru, There is a mosquito in the bedroom), as opposed to 冷蔵庫にビールがある (Reizōko ni biiru ga aru, There’s beer in the fridge). Another particle the two Japanese “to bes” frequently attach to is に, in which case the point is not that there is something, but where that something is, as in 蚊は寝室にいる (Ka wa shinshitsu ni iru, The mosquito is in the bedroom) and ビールは冷蔵庫にある (Biiru wa reizōko ni aru, The beer is in the fridge).
A third important “to be” phrase is である (de aru). Better known in its formal disguise です (desu), it makes up a large part of Japanese formal speech. It can be further upgraded into でございます (de gozaimasu), as in サザエでございます (Sazae de gozaimasu, I’m Ms. Sazae) from the much-beloved Sunday evening TV program.
It goes without saying that iru has its upgrades too. When talking about others, it commonly turns into an exalting いらっしゃる (irassharu). By contrast, one’s own humble existence is lowered with おる (oru). Just compare 現在どちらにいらっしゃいますか? (Genzai dochira ni irasshaimasu ka, Where are you presently?) with 現在海外におります (Genzai kaigai ni orimasu, I’m presently abroad).
A nightmare for language purists is the form おられる (orareru). It’s based on humble oru, but in the elevating passive mood, which must appear like a contradiction per se. However, the form is in fact far too common to be branded as wrong. Thus, in official surveys, more than half of the respondents said they generally do not take issue with sentences like 総務の武田さんは、どちらにおられますか? (Sōmu no Takeda-san wa, dochira ni oraremasu ka?, Where is Mr. Takeda from General Affairs?). One likely reason is that in many Japanese regions west of the Kanto line, oru is used in the simple sense of iru, with no implications of humbleness whatsoever.
One existentially important function of iru is to express actions that happen continuously over a longer stretch of time, in a similar way to the English progressive. For instance, 今食べている (Ima tabete-iru) describes someone who is presently eating, as opposed to 今食べる (Ima taberu), which means that someone is about to eat but hasn’t started yet.
Not quite like in English, iru is also used to foreground the result of some action. Thus, パソコンが壊れている (Pasokon ga kowarete–iru) is not an attempt to verbally capture my computer during the process of going up in flames, but it’s the simple — though painful — observation that it’s broken. Busted. Kaput.
Where the result of an action has been intentional, aru comes back into play. The difference can be easily understood when we compare the nonintended state of affairs in 木が倒れている (Ki ga taorete-iru, the tree has fallen down) with the premeditated tree slaughter in 木が倒してある (Ki ga taoshite-aru, The tree has been felled).
But the most amazing thing iru can do when combined with another verb is to provide hints about the agent of that verb. The basic rule of thumb is that the simple tense is used to describe actions done by the speaker, whereas an iru progressive, frequently in its past form いた (ita), communicates that the action has been performed by someone else.
The tendency is most salient in reported speech, which can be indicated either by the simple と言った (to itta) or progressive と言っていた (to itte-ita). While both basically mean “said person X,” a recent study shows that the X in the simple form will most likely be the present speaker, whereas the X in the progressive version is some other person.
In closing, you might want to know which of the many “be” options was chosen for the Japanese version of Hamlet’s famous soliloquy. Well, Hamlet’s Japanese alter ego staunchly refused to raise the “to be” issue in the first place, rephrasing it instead as いったい どうしたらよいのか (Ittai dō shitara yoi no ka, What on earth am I supposed to do?).
As is well known, he couldn’t make up his mind right up to the very end — at which point he turned from animate to inanimate.