How can I finally understand the confusing modal verb "мочь"?

Question

The verb мочь is one of the most basic words, actually a central modal verb, but I am so much confused about it. I am often at a loss as to how to interpret it in particular sentences, and I avoid using it when I write and speak in Russian. I am overwhelmed by inconsistent examples of its use and by how it drastically changes its meaning. To me, this verb is like a wild animal I cannot tame.

This verb may be so natural to you that you have no idea how I could be unable to understand it, but I apparently have different thinking patterns, as I belong to a very different culture.

I would like to humbly explain you my difficulties in understanding this verb and to kindly ask you to explain this verb in a way tailored to my difficulties.

I would like to start with the following sentences, which I just found in Google as illustrative examples:

(1) "Никто не может подвергать опасности жизнь своего ребенка, или других детей, — заявил губернатор, — а в случае с корью сложилась именно такая ситуация, когда поведение одних угрожает здоровью других." (Source)

(2) Роман Абрамович может за один раз доставить на своей яхте в Крым до 3000 отдыхающих. Может, но не хочет. (Source)

(3) Потому что он человек долга, - ответил Гарман. - Он не может предать свою батарею, не может предать свою полусумасшедшую жену и своих девочек. (Source).

(4) Савченко может выйти на свободу в ночь на 15 апреля. (Source).

(5) Окружающие считают Карла Уорнера слегка странным: он может часами разглядывать овощи в супермаркетах. (Source).

(6) Не забудьте написать ваше имя и, да, вы можете пользоваться калькуляторами, - говорила миссис Ланкастер, раздавая листочки с тестом ученикам. (Source).

In these sentences this verb appears to mean entirely different things: In the first sentence it appears to mean an ethical norm, in the second - a physical ability, in the third - a character quality, in the fourth - a possibility that cannot be excluded, in the fifth - habitual behavior, in the sixth - a permission.

With such a great span of the meanings, I am at a loss as to what the concept of this verb is and what else this verb can mean. English has separate modal verbs for ability and possibility - can and may, respectively; ethical norms are expressed in English rather by using the modal verb should, and habitual behavior - rather by using the modal verb will.

Whilst in sentences (1)-(6) the meaning of может is more or less obvious to me from the context, in many other cases it is not. To illustrate this, I would like to show you an example that made me seriously puzzled some time ago, when I browsed the Internet to see what the Russians think about the Northern Territories. This is the title of a material published by Radio Svoboda:

(7) Может ли Путин передать Японии 2 острова Южных Курил? (Source)

If you follow the link I provided, you will see that there is no context at all and that this question is used in a survey, so the question as it stands by itself must be very clear to every Russian, but how could it be clear if может has so many very different meanings?! What is this question about - an ethical norm, a physical ability, a character quality, or a possibility that cannot be reasonably excluded? In other words, which of the following interpretations is most accurate:

(7a) Does Putin have a moral right to transfer two islands of the Northern Territories to Japan? (For example, a moral right in regards to the inhabitans of the islands or the whole population of Russia.)

(7b) Does Putin have enough actual power in Russia to transfer two islands of the Northern Territories to Japan if he just decides to do so?

(7c) Is Putin wise, stupid, brave, unscrupulous, or backboneless enough to be capable of deciding to transfer two islands of the Northern Territories to Japan?

(7d) Can't it be excluded that Putin actually transfers two islands of the Northern Territories to Japan in the future (for example, as a result of some possible geopolitical or economic event sequence that may prompt Putin to transfer the islands in exchange for something)?

How do you understand Question (7) and why?

Let's assume that Putin can easily transfer the two islands to Japan if he just decides to, but is absolutely resolved not to transfer. How should I then answer Question (7) - да or нет?!

Now let us consider the following example, which is the title of another article:

(8) Непобедимый Чапаев: тайна гибели легендарного комдива. Мог ли он выжить? (Source)

This title must be very clear to every Russian already by itself because it is a title, yet I got puzzled as to which of the following two intepretations is correct:

(8a) Invincible Chapaev: The mystery of the legendary commander's death. Could he have survived?

(8b) Invincible Chapaev: The mystery of the legendary commander's death. May he have survived?

Question (8a) is whether he had an opportunity to survive, that is, about a missed opportunity, whilst Question (8b) is whether it cannot be excluded that he actually survived, that is, about a possibility.

My original interpretation was (8a), because the title contains the word гибели suggesting that the very fact of his death is not disputed, but I proved to be wrong. Reading the article itself, I realized that the author writes about conspiracy theories in which Chapaev survived. So yet again I was tricked by this wild verb, which I just cannot "domesticate."

What adds to the mystery is that there is an article entitled "Мог ли СССР выжить?" (Source). This title has the same grammatical construction, but the opposite meaning, as we know that the USSR did not survive.

So how could you explain this wild verb to a learner who is eager to finally tame it? What is the exact concept behind it, the concept that logically unites so many entirely different meanings under a single umbrella? And how do you always succeed in unmistakenly interpeting this verb, especially in sentences like the above ones about Putin and Chapaev?

Answer 1

As pointed out in comments, your impression of English “can” and “may” seems too rigid. Consider these dictionary definitions with the many meanings and examples, some of which overlap, and the usage note at can: can, may, may.

Many of your original examples can use these same English verbs and sometimes even both, even though you say they all of the examples have different meanings:

1. OK, I guess in such an official context this one has to be “should” or “must (not)” or even “has the moral right to” or even just “has the right to”—with the “moral” being implied!—in English. But informally, you might exclaim, “You can’t put your child in jeopardy!”

2. Roman Abramovich can/could take 3000 people on his yacht to Crimea at a time. He could do that, but he doesn’t want to. (The most direct translation of “could” back into Russian is “мог бы”, and it could work in the original Russian phrase, too. At the same time, “can” technically works here in English. But in Russian, “может” here sounds perfectly natural whereas I feel “can” sounds odd in English, and “может” has the benefit of providing a better artistic effect by matching the case of “не хочет” exactly.)

3. He can’t betray his battery, and he can’t betray his wife and girls. (He feels he doesn’t have a moral right to do so. But his morals are such an integral part of him that he feels he is unable to do something morally wrong.)

4. Probably: Savchenko may get out of jail on that night. But it might also be “can”. Really, to fully understand the exact meaning, you’d have to read the full article. The only information the title gives you is that one way or another, it is possible that she will get out of jail on that date.

5. I like your use of “will” here, but equally well he can spend hours looking at vegetables in supermarkets, especially if he doesn’t do it every day, or he even may spend hours to just look at vegetables in supermarkets. To be honest though, I think the most natural English phrasing of this sentence would just use present simple: he spends hours looking at vegetables.

6. You may/can use calculators. As noted by Oxford Dictionary in the above links, it is most traditional/strict/formal to use “may” to give permission, but in reality, “can” is also possible (in speech of all registers) and means the exact same thing.

I’m guessing your confusion really stems not from the English verbs, of which “can” actually matches мочь fairly closely, but from the variety of forms used in Japanese to express these nuances. Off the top of my head, there’s 〜事ができる denoting physical ability, 〜ていい denoting permission, 〜可能性がある denoting a chance of happening, 〜かもしれない denoting the speaker’s lack of knowledge of whether something is/was/will be happening, and 〜える expressing other states of being able to do something (with some overlap with できる) or object states where something can be done to them. These are all мочь in Russian, except inherent, passive object states such as “edible”/“съедобный”. Any time you want to use any of these, be bold and just use мочь.

Of course, if you want to emphasize a particular nuance, it is possible in Russian by using additional words: я не умею; разрешено/можно; есть шанс/надежда, что…; возможно/может быть, [что]…

As I’m sure you know from Japanese, context is king. When multiple meanings of мочь work in a context, you either guess (possibly incorrectly) or the speaker simply doesn’t consider it important enough to differentiate between them. The common meaning is that the effect may end up occurring, one way or another. Is it because the subject takes an active action to cause it to occur? Is it because something else acts and enables it to occur? Is it because something else doesn’t counteract and prevent it from occurring? Is it because people think it should occur? In most cases, it’s either clear from the context or doesn’t matter.

Now, what about the Putin example?

7. All of them.

   I’m not even sure, but I think the very first meaning that crossed my mind was “is it likely that he will do so in the imminent future?” (7d) but immediately afterwards I thought of “should he?” (7a, I guess).

   If I was asked this kind of question (except if I was in a hurry or wanted to avoid a detailed answer for some other reason), I’d give an answer that essentially consists of several parts that answer each possible meaning that I would have an answer for. For example:

   Может-то он может* [this is 7b, actually, which I processed without even thinking!], но вряд ли он это сделает (в ближайшем будущем, по крайней мере) [7d]. Честно говоря, я думаю, что их следовало бы отдать/оставить по таким-то причинам… [7a] но в любом случае, сейчас, насколько я слышал, никто их отдавать не собирается, так что пока что непохоже, что это произойдёт [7cd], если только японцы вдруг не предложат что-то кардинально новое, но непонятно, что такого они могут предложить.

   * Now that I think about it, I don’t actually know if he can/if this depends on Putin personally. Let’s not go there. This was just an example.

   I notice that I used могут myself in my example answer. Which meaning did I put into it? Essentially, this могут has all the same meanings as the original может in the Putin question. I didn’t actually think about any particular meaning when using the word. In English, I’d use “can” and equally not think about the exact meaning.

   But if I now try to figure it out in retrospect, I guess it’s “unclear whether there is anything the Japanese are willing and able to offer to the Russians that would actually be so beneficial to them that they would be happy to trade the islands for it despite the public backlash (if it wouldn’t change the public opinion as well)”.

   Well, what’s “willing and able”? We can keep going further/deeper with these questions, and at this point I think the exact meaning already doesn’t matter to the verb I chose. If I had wanted to underline a particular concern to the Japanese, I would have spoken of it explicitly in the first place. I think in this case the most important factors are physical ability (what at all could the Japanese offer that the Russians would find useful, even if they entirely disregarded public opinion within Japan?) and public opinion/political consequences, especially in internal politics (if they do offer that, will they be shunned by voters and fellow politicians?), but I’m not forcing this choice upon the other person, and if they think other factors are more important, that’s fine too.

Of course, with such an overloaded word as you point out, there are bound to be cases when misunderstandings do occur:

8. My original impression was the same as yours:

   He died, but could he have done something differently to survive instead?

   Indeed, this might be even more specific than your understanding. See how “Could he have survived?” has several meanings too; at least these two:

   • Could he have done something differently to survive instead of dying?

   • Could something else have happened to let him survive instead of dying?

   My mind jumped to the possibility of his own actions because it seemed (to me, at that time) most sensible in the context, but this is not by any means implied by the verb itself. Indeed, other Russian speakers might have thought of the other option or neither in particular.

   If I were to read the article, I’d most likely be surprised to discover the author intended the meaning “Is it possible that he actually survived when everyone thought he was dead?”. But I wouldn’t think the author had used erroneous phrasing. At most, I might think that the author had deliberately chosen this phrasing to lure people who shun conspiracy theories into reading the article by capitalizing on the fact that most people would interpret it the same as we did. The same can be done with any other word that has multiple meanings or homonyms/homographs, in any language. If you read a lot of articles by authors who do this in a particular language/manner, you start to recognize ambiguous titles before clicking on them and ignore such articles or know what to expect when you do open them out of curiosity. But it is also entirely possible that, when the author was choosing the title with the intended meaning already in mind, this phrasing seemed completely natural and they didn’t realize other people would misinterpret it out of context.

So misunderstandings can occur sometimes, but don’t let this stop you from using the word!

Moreover, the multiple nuances can even be used intentionally to humorous effect: e. g. the sentence above said Abramovich can take 3000 people on his yacht to Crimea. Does this mean his yacht holds 3000 people, or that he is allowed to take people to Crimea? Probably both. But what if one is true but not the other? Тогда он может, но не может!

Furthermore, actual everyday dialogue can intentionally contrast multiple nuances in a somewhat similar manner:

— Возможно, твой друг может это починить?
— Не может: у него болит спина, и он не выходит из дома.

— Мы можем забраться на их яблоню и оттуда пролезть в окно второго этажа!
— Не можем, потому что яблоня огорожена забором.

— Говорят, он может часами смотреть на овощи в магазине.
— Не может: ему месяц назад запретили входить в продуктовые магазины.

Answer 2

For a person (and in Russian everything is a person), the Russian thought model makes no distinction between:

1. the person's moral right to do something;
2. the person's ability to do something (like, physical ability);
3. the objective circumstances allowing or not for anyone to do something in a given situation. (Note that the circumstances are a person too!)

Raskolnikov's famous "Тварь я дрожащая, или право имею?" perfectly illustrates how he makes no difference between (1) and (2).

Another perfect example of the same ambiguity between all three usages is found in a genius play "Дракон" by Шварц. In one of the final scenes the hero (Ланцелот) lies wounded at the side of the 3-headed Dragon he just slayed (the Dragon is barely alive).

 2-я  голова. Тише! Я чую, рядом кто-то живой. Подойди. Дай воды.

 Голос Ланцелота. Не могу!

You really can't tell whether the hero has no moral right to help his enemy, has no ability to do so (as he is wounded too), or something else is preventing him from doing this!

That shows us the hero's personal integrity. For a true hero, there is no difference between thought, action, and evaluation of external circumstances.

(Yep, that means that the journalists represented Putin as a true hero in the islands story ;-))

Answer 3

Есть известная максима о том, что язык определяет мышление. Все различия между оттенками значений в данных случаях должны быть ясны из контекста (либо по интонации). Если это не так, то и самих отличий тоже нет. По крайней мере для человека говорящего и думающего на русском.

Например, (8b) просто не имеет смысла, если вы только не любитель "теорий заговора", ну или же горячий поклонник творчества Пелевина ;-) Поэтому (и только поэтому!) данный вопрос будет понят в смысле (8a).

Что же касается (7), то это вопрос о будущем, а значит обо всём сразу (не столько о Путине, сколько о том, может ли такое случиться вообще). При этом, разумеется, значение (7d) должно быть релевантно в наибольшей степени, а (7a) - в наименьшей. Однако подобная многозначительность в формулировке вопроса явно появилась неспроста. Это по поводу Ваших сомнений, высказанных в комментариях - никто не ошибается так часто, как журналисты, но, по крайней мере часть их ошибок совершается преднамеренно.

Answer 4

1.

Может ли Путин передать Японии 2 острова Южных Курил?

I understand it in the sense of possibility which can't be excluded. Whether it's probable that he decides to cede them and does so, i.e.

(7d) Can't it be excluded that Putin actually transfers two islands of the Northern Territories to Japan in the future?

I guess it's because (according to my observations) survey questions which deal with moral character and integrity of political leaders are framed more explicitly and because ordinary citizens are not considered to be in a position to question his political powers and rights, these are a given. So the remaining interpretation is whether he will actually use his authority.

I watched the video to see how respondents had understood the question. About a half used the word должен/должно either in the positive or in the negative. It could mean that what they had in mind was that he might but should not (it's not excluded but i prefer that he not). But frankly i failed to figure out how they'd exactly understood it in part because quite a few of them instead of judging chances of cession by Putin offered their opinion on whether such cession is acceptable at all. Still in the dialogue with the 1st respondent the journalists asked a clarifying question почему не может быть? which indicates a future possibility. So this seems to give an idea at least on the intent of the journalists themselves. And the last respondent seems to have understood it similarly.

2.

Непобедимый Чапаев: тайна гибели легендарного комдива. Мог ли он выжить?

I would have understood it like you did.

(8a) Invincible Chapaev: The mystery of the legendary commander's death. Could he have survived?

just because i've never heard of such a conspiracy theory to consider it in the possible reading, but if i have to me it would have sounded ambiguous. If the author were aware of the ambiguity or more considerate towards the readers he could have rephrased it to read something like Не мог ли он выжить? Что, если он выжил? or even more explicitly Действительно ли он погиб?

And how do you always succeed in unmistakenly interpeting this verb, especially in sentences like the above ones about Putin and Chapaev?

Well, as follows from my reply this may not necessarily be always the case. Often you just don't give it too much thought and simply dive into the content to find out. In a dialogue you might ask for clarification. But of course in most cases it's pretty clear because, i think, the natives both as speakers and as audience rely on a complex of clues stemming from familiarity with certain established use patterns and situations, where one specific meaning would be dominant or the most likely, as well as from the context of a speech act.

As for the concept behind the verb, at this point i'm not ready to give any opinion or thoughts, because it's a complex and intricate subject. What i can say though it that it just appears to be polysemous. Such status of Russian modal verbs is recognized by linguists (and i believe it's not exclusive to Russian)

Answer 5

How comes none of the answers was marked? Anyway, here is a friendly beginner's survival guide to the almighty мочь (pun intended; "мочь" is also related to "might" and "power" - "мощность", "сила")

(If you didn't ask for a learning methodology and only need a rational explanation about the word's numerous, contradicting meanings, please scroll down to paragraph 5)

1. Accept the problem

Bad things happen, Russians use the same lexical unit to express loosely related, distant categories. Can/able translates into мочь, may/admissioned translates into мочь. And possibly/probably/presumably too. I guess you've passed this stage already.

2. Relax

All Russian students have the mirrored head ache. They have some great time understanding why English people use so many different words - where Russians accustomed to use a single one. In both cases the problem is resolved through addiction and habbits (see below). You're not stupid. Langauge is. Think of it as irrational and habit-driven by default.

Each language comes with a bag of ugly distortions which can only be accepted after some time. You can't digest it in a flash. Let it flow naturally.

3. Practice constantly

You brain will eventually re-wire to use the word properly - even without truly understanding the underlying reasons. Most Russians are absolutely helpless about the problem you've raised. Seriously, you'll knock out nearly anybody with it. It's an academic issue most mortals aren't aware of. A centipede will stumble the next moment you ask how does it control so many legs.

Our brain is not super-good at rationalizing, it's best feature - mimicking what it witnessed. Let go the understanding urge. You may or may not aquire it over time - it is not directly related to successfull ability to correctly and fluently use a language. Statistics are on your side here: a foreign language is not a crypto-system and it wasn't designed to resist you.

If you keep reading and using the language (emphasize on problematic patterns, storm the examples of "мочь" regularly), it will inevitably find its way into your mind, and you'll be thinking in Russian in no time. The real issue is the switch between the 2 different thinking patterns, but that's off topic.

4. Comfort yourself with rationale

Think of learning the rational reasons and the rules as a secondary activity, developing your individuality. Knowing why Russians use мочь in seemingly unrelated cases won't help you much in pursuing practical short-term goals. As you grow more accustomed, those overcomplicated rational explanations will fall into place easier.

5. Break the problem into large categories

If you still read this and plan to go all rational against my advice, I propose to divide the examples you offered into 3 groups to grasp the underlying consistency (which you stated remains ellusive to you):

• Group A, where мочь denotes an inner ability and willingness;
• Group B, where мочь implies a dependency from others;
• Group C, where мочь is an ugly, nasty shortcut for a hypothesis or speculation statement

Isn't that easy? Let's try to recognize the particular group in your examples:

1) Group B. The society prohibits harming children. Suggested translation: "Nobody is allowed to put children in danger..."

2) Group A. The man is totally able and self-sufficient, but lacks any motive. "Can ..., but doesn't desire to"

3) Group A. Again, it's about man's internal decisions and reflections. "He just can't betray his people..."

4) Group C. The speaker blatantly speculates, basing on rumors or some insider's data. "Savchenko might be freed on 15'th..."

5) I'm sorry, it's an exception, an idiom. You've been unlucky to hit it and ruin yourself a day. It is equivalent of: "бывает, он часами разглядывает" or simply "он часами разглядывает" (the latter is too blunt, unexpressive). This idiom is used to better express the typical case of present simple tense, as the language simply lacks auxiliary verbs for that.

6) Group B. Students got a permission. It's not their decision, they're recipients of someone's favor. "You are permitted to use..."

Feel free to add more examples. It is totally possible I forgot some usage group. Like I said, a natural speaker uses the language on an everyday basis without rational, exhaustive awareness of its distortions and features.

5.2. Recognizing/emitting the Group C

My wild guess is that Group C bugs you the most. (For this reason I omitted the paragraph 5.1, which should have explained how to distinguish between groups A and B; other answers offer an exhaustive insight on that. Leave a comment if you'd enjoy any clues on that too).

The grammatical form "[X] может [Y]" in the Group C is an unfriendly shortcut for: "[X] возможно совершит [Y]" or "[X], может быть, совершит [Y]". The ellusive мочь here is just a reduced remnant of возможно (possibly). The ability and possibility categories are rather loosely related philosophically. Russian language derives those from the same root.

To discern this case from Groups A, B, look at the context of the sentence. In a speculation statement the predicate может is not related neither to subject's will/ability, nor to permissioning to execute the action. The sentence would simply lack such information.

Back to example 4). Does she want to exit the prison? Not stated. Can she do it on her own? Unknown, but unlikely - otherwise the news would scream of a jailbreak, not simply может. Somebody gave her a permission? No, we can't tell from the sentence alone! Ergo, it's only speaker's opinion on what might happen. The statement is in fact so obscure and logically non-binding, that you can't tell if she is going to be freed at some other day or not freed at all!

The statement is not about her will or ability; neither it gave any clue as to who in particular is responsible for setting the date, whom she depends on. It's only an assumption about something, not ability/disability, nor will, nor anybody's participation or admission.

Emitting group C is pretty straightforward. "You might stumble on this cable" - "Ты можешь споткнуться об этот кабель".

5.3. Recognizing/emitting idioms

See paragraph 3. Idioms can't be ruled out, you just have to get accustomed to them through repetition. I'm sure you'll enjoy it. Also I couldn't list them.

6. How to translate to English

Translating Eng->Rus is not an issue for you, isn't it? Basically, you just replace can, may, might, possibly (with a verb), allowed, permitted etc. - into может. No big deal. (Surely you know what to do with cannot, denied, unlikely, not allowed, etc.)

I've already discussed emitting Group C and exceptions.

Group A's мочь typically translates into can, is able.

Group B's мочь behaves more sophisticated in the English, in my opinion. You always have safer options to translate it to permitted to, allowed to. But choosing between may and can is not always rational. Normally (as explained in student books), one would convert to may, but...

Please refer to example 1). You can translate to: "Nobody is allowed...". But would anybody say: "Nobody may hurt children..."? I guess not. And I don't know why, it's just an empirical impression whispering in me, insisting to say: "Nobody can hurt my children!" You see what I meants in the paragraph 3? My brain pushes me in the right direction, but I don't know the reason behind it.

English is being more sophisticated here. In this example the context is clearly about denying a permission, the society puts some restrictions; it doesn't discuss somebody's unwillingness. Well, I never said those logical groups I proposed are equally good for both languages! After all, you asked to understand a Russian word, not to find a perfect English counterpart. I hope this helps.

Advanced tricks

How to lie using surveys and statistics

When people can't understand the context of a question, they either (rarely) counter with a refining question to restore the context, or (more commonly for a busy random stranger) imply a context of their own taste. Something which corresponds best to their current mood. Please check the Russian word додумать.

One can use ambiguous phrasing to subtly bias people into picking the (secretly) anticipated answer. The goal of a survey is usually to make an illusion of people's opinion. Example 7) shows such exploit in action. The phrase is simply ambiguous and that survey's results in question should be ignored. It's a trash data, collected specifically to accomplish some political trick.

You can't infer the meaning of мочь in the example 7), because it was the purpose: deliberately asking an ambiguous phrase to trick people. People were caught off-guard on a street and didn't have a chance to think about the question and the consequences of their choice. So you're right about overthinking this case; but it wasn't meant to be answered objectively.

To summarize: nobody could precisely understand the question 7).

Answer 6

1. I probably would translate such titles not with a modal, but with "be".

"Может" in this context can be understood as a shortened version of "Может быть" - "may it be/is it possible".

I would translate these titles as

"Is it possible that Putin will transfer to Japan 2 islands of Northern Kuril"?

"Indefeatable Chapaer: Is it possible that he survived?"

The "Может" in this context is more of a clickbait technique designed to be ambiguous - introduce some possibility, but not really explain the context or the real meaning behind it. I can't imagine a scientific or even a respectable article with such a title.

2. I think it's a good rule of thumb that if in doubt, it's better to assume the meaning of "is it possible that something will/did happen" - for any reason.

Answer 7

As a bilingual Russian-speaker (in addition to Ukrainian) and a native habitat of Ukraine (post-soviet country) I will try to explain this:

"In these sentences this verb appears to mean entirely different things: In the first sentence it appears to mean an ethical norm, in the second - a physical ability, in the third - a character quality, in the fourth - a possibility that cannot be excluded, in the fifth - habitual behavior, in the sixth - a permission."

For example, you can not do smth because your morality, physical disability, external prohibitions stop you and you are unable to do smth (it is mostly about sentences 1, 2, 6). Sentence 3, as for me, is also about morality, but your explanation is also correct. Also, as you have mentioned about sentence 4, can can also have a meaning of may/might, which seems not strongly different from the word 'can' in my perception. While learning English, we usually learn, that "might" is a very low probability, "may" is relatively low (like 30% or a bit more), "can" is more (like 50+), "must" is very high (80-90+). About sentence 5 - I think can is used here, because most people (or at least the author/character/speaker/writer) can not do that, because it seems very untypical, the person may/can get bored, tired, consider it like ridiculous, insane, out of common sense etc.

About sentence 7 - I think your suggestions are grammatically correct, in addition I give an example of how I understood the sentence (most of them are close to 7d, 7c) " Is it possible? Do the external circumstances force/allow him to do that? What profits he/country can/may/might get of it? Do they overweight the disadvantages of the decision? Isn't he too proud for it?".

About sentence 8 - I think that the word mystery (of death) in the sentence may guide the person's thoughts that it can be some conspiracy. And the sentence "Мог ли СССР выжить?" has no clue about any conspiracy, but when reading Russian titles of news or articles you never know - there is a tendency to make clickbait titles, which can trick your mind, sometimes titles are almost a lie or (more rarely) a real lie. An example of tricking is the youtube video with the title "Афроамериканец наехал на украинца в США", which is usually understood like "Afroamerican ran over an Ukrainian (a person) in the USA", but actually in the video afroamerican driver hit a car droven by an Ukrainian.

Answer 8

I will try to explain it in a simple way.

In Russian verbs мочь и должен describe a situation person ended up in, not the person himself or his attitude. And it doesn't matter why said person ended up in this state. So мочь is closer to english word "able", than to "can" or "may".

While it may be silly to say in English "Is Putin able to transfer two islands to Japan?" - it is the logic of a Russian languge (there are a lot of subsences and inclines, wich are commonly translated with "may" or "can" words, but they are "next level of understanding")

Same story with "должен" word. I do not know neutral anolog in English, but just keep in mind that Russian (and other europian languages) has little or no "second plain of meaning" and more direct than eastern languages.

P.S. On second thought, the most exect translation of (7) is: "May it happen that Puttin will transfer two islands to Japan?". And for "Забор не должен упасть" - "It must not happen that the fance falls".