but do most other languages use the same word for “should” in all three of those sentences?
I suppose yes (data points: Slovak, Esperanto).
Seems to me that although the reasoning why anyone “should” do the thing is different in different cases, the expected outcome is the same—the sentence is spoken to create a social pressure on the listener, to increase the probability that the listener will do the thing.
Thus, the presssure on other person’s behavior seems like the essense of “shouldness”, not the justification. (Even the special case of “I should” is probably applying the social rules to oneself, either to remind oneself that other people would want them to do that, or simply to re-use the existing mechanism of altering a person’s behavior.)
the sentence is spoken to create a social pressure on the listener
How does it do that? Only indirectly, through what it means to the speaker and listener. What does it mean? That is the question here, and “social pressure” is not the sort of thing that can be the answer.
I suppose yes (data points: Slovak, Esperanto).
Seems to me that although the reasoning why anyone “should” do the thing is different in different cases, the expected outcome is the same—the sentence is spoken to create a social pressure on the listener, to increase the probability that the listener will do the thing.
Thus, the presssure on other person’s behavior seems like the essense of “shouldness”, not the justification. (Even the special case of “I should” is probably applying the social rules to oneself, either to remind oneself that other people would want them to do that, or simply to re-use the existing mechanism of altering a person’s behavior.)
How does it do that? Only indirectly, through what it means to the speaker and listener. What does it mean? That is the question here, and “social pressure” is not the sort of thing that can be the answer.