Должен is one of the most fundamental Russian modals and is impossibly difficult for me, even more than the modal мочь was before I asked here a question about the latter. I received so thoughtful, useful, and inspiring answers about мочь that I got strongly tempted to ask about должен in order to get as enlightened as I got about мочь and in order to better understand your wonderful language and your unique way of thinking.
Giving in to the temptation, I am now bashfully describing my tremendous difficulties with the modal должен and humbly asking you to explain this modal in a way tailored to my difficulties. Please kindly do not judge me too harshly for my inability to understand this fundamental Russian modal, because it is apparently my cultural ways of thinking that are preventing me from understanding it.
I would like to start with the following sentences, which I just found in Google as illustrative examples:
(1) Сань, не уходи, не бойся, он не должен сломать вольер! (Source)
(2) Всего до конца года Россия должна выплатить МВФ более трех с половиной миллиардов долларов по ранее выданным кредитам. (Source)
(3) А вот граждане просто не должны давать взятки. Тогда и брать будет нечего. (Source)
(4) Если кто-то хочет получить от врачей в больнице квалифицированную медицинскую помощь, то он должен дать взятку, так как система бесплатного медицинского обслуживания финансируется не в полном объеме. (Source)
(5) "Если главный редактор Константин Ремчуков берет деньги за выход статьи в "Независимой газете", он должен сидеть в тюрьме", – заявил 16 марта в эфире радиостанции "Эхо Москвы" председатель совета директоров Mirax Group Сергей Полонский. (Source)
In these sentences the modal должен appears to behave like a super chameleon that changes its color to the most drastic extent. In the first sentence this modal appears to mean a conviction that something will actually happen (with negation in this particular case), acting as a future tense modal, in the second - a debt, in the third - an ethical norm, in the fourth - one's own necessity from the practical standpoint, and in the fifth - the order of things. Sentence (3) says that people должны not bribe, whilst Sentence (4) - that they должны bribe, and Sentence (5) - that they должны get imprisoned for that. Being both puzzled and amazed, I cannot understand how you manage to express everything by one single word.
I am so much confused about this. In my culture, 義理 and 人情 are absolutely opposite things and correspond to precisely opposite feelings with respect to each other, being like the North and South Pole on the globe of feelings, but you seem to express the sense of duty to others and the opposite feeling (the sense of internal need) by one and the same word. For example, in Sentence (3) the modal должен appears to express the sense of duty to others, whilst in Sentence (4) - the sense of internal need. Furthermore, typing he must, he should, and he owes in Google Translator, I get one and the same translation to Russian, oн должен, and three different translations to Japanese. Given that words are connected to feelings, I cannot imagine how so different feelings can be expressed by one and the same word.
It is only thanks to the very telling contexts that I apparently managed to understand Sentences (1)-(5), and I often cannot understand phrases with должен even despite my best efforts. I would like to show you a few examples of such situations.
(6) Должен ли парень платить за девушку на свидании? (Должен the guy pay for the girl on a date?)
This question, with slight variations like должен ли мужчина платить за женщину or должен ли парень платить за девушку в кафе, is often used as a title or a survey question and therefore must be clear to every Russian as it stands by itself even despite that there is no context whatsoever besides the guy, the girl, a date, and paying.
To explain you my confusion, I would like to show the first three interpretations that came to my mind:
(6a) In the ideal order of things, does the guy pay for the girl on a date, or what does the sense of fairness suggest?
(6b) Do the existing cultural norms prescribe paying for the girl on a date?
(6c) Considering things from the practical standpoint of the guy's interests, that is, from the standpoint of increasing chances of successfully starting a good romantic relationship with the girl, is the guy's best course of action to pay for the girl on a date, given the actual mentality of girls?
In Interpretation (6a) the person to whom Question (6) is addressed is offered the role of judge, whilst in Interpretation (6b) - of cultural guide, and in Interpretation (6c) - of the guy's adviser. These three interpretations reflect, respectively, the sense of fairness, sense of duty, and sense of inner need.
Given the huge differences between the interpretations, I got puzzled as to which is correct, but apparently none is, as I realized when I read how Russians answer Question (6):
(6d) Я считаю каждый уважающий себя парень должен заплатить за девушку. (Source)
(6e) Тем не менее первая встреча бывает во многом показательной, поэтому у обеих сторон может возникнуть понимание, что продолжение отношений вряд ли возможно. Но это не является поводом, чтобы девушка доставала кошелек и оплачивала счет в ресторане. Уважающий себя мужчина и в случае неудачного рандеву будет действовать в рамках правил хорошего тона. Ответ на вопрос, должен ли парень платить за девушку на первом свидании, однозначен: да. (Source)
These answers suggest that the question is about self-respect and sounds to Russians as:
(6f) Does a normal guy have enough self-respect to feel obligated to pay for the girl on a date?
But I am still very unsure, especially because I saw an article that gives the following answer:
(6g) Как и во многих утверждениях по типу «парень должен» — парень не должен. Ты можешь заплатить за девушку, а можешь не платить. Правила, по которым ты определяешь «платить или не платить», определяешь ты сам. И придерживаешься их потом. Да, вот это одно из немногих утверждений по типу «парень должен», в котором парень действительно должен. Парень должен придерживаться правил, которые он установил для себя сам. (Source)
This answer made me very puzzled. This truly mind-blowing logical construction with five должен and two можешь may be a key to understanding how должен works in the Russian way of thinking.
I am aware that in English it is often asked, Should the guy pay for everything on a date, but the original Russian question (6) appears to mean a different thing, as I never saw English-speaking authors answering in terms of self-respect or obligation. They rather give advice. I humbly guess a proper Russian translation of the English version is стоит/следует/советуете ли парню платить за девушку. The question with должен appears to be about something different, but I am unsure what it is.
The list of phrases I do not understand goes on and on:
(7) Почему каждая женщина должна уметь флиртовать: мужской взгляд (Source)
(8) Должен ли Путин уйти? (Source)
(9) Я должна была быть мужчиной (Source)
And so on. How can I learn to interpret such phrases? Phrases (7)-(9) are titles and must be clear by themselves, but are very puzzling for me. In Phrase (7), is должна an expectation of the author about women, a need of women, a wish of men, advice to women, the ideal order of things, or what? In Phrase (8), is должен a prediction, advice to Putin, an ethical necessity, or what? And Phrase (9) made me especially puzzled - I should have been a man, I must have been a man, I had to be a man, or what does it mean?
Another part of my difficulties with должен is that with this modal meaning everything in Russian, I am unsure how I can make proper Russian translations of thoughts like this one:
(10) People shouldn't bribe, but sometimes they must. If the bribe is accepted, the bribe taker owes it to the bribe giver to help him in a way in which the bribe taker shouldn't or isn't obligated to help. If the bribe taker accepts the bribe but refuses to help, and if the bribe giver is backed by mafia, its members then have to explain the bribe taker that he must do what he owes to the bribe giver.
Using должен everywhere in a Russian translation of Text (10) would make no sense, so I am at a loss as to how I can properly translate Text (10) to Russian as succinctly as possible, without expanding the text by tedious explanations.
Could you explain this impossibly difficult modal должен in a way tailored to my difficulties? I humbly hope to get enlightened by your wisdom.
UPDATE: Prompted by the respected user @shabunc , I am clarifying precisely what I want to ask: How do you understand the concept of this modal in terms of meaning, feelings, and/or way of thinking, the concept that logically unites so many entirely different meanings under a single umbrella, and manage to unmistakenly interpret this chameleon-like modal in expressions like Phrases (6)-(9) and to make precise but succinct Russian translations of texts like Text (10), which contain various English verbs corresponding to different meanings of должен - should, must, owe, be obligated to, and have to? [If possible, I would like to see a cut-and-dried concept of this modal and how this concept works for Phrases (6)-(9).]