Which do you use? “Shall?” Or “will?” Personally, I don’t use “shall” much at all.
When I was in school, and this was many years ago, I was told that “shall” was used in the first person only, while “will” was used in second and third person. “I shall…” or “We shall…,” in contrast to “You will…,” or “He will…,” or “They will….” But even then, that advice seemed inconsistent with how I heard English being spoken. I never used “shall” much at all, and no one I talked to did either. It sounds funny to hear someone say “I shall….” It’s immediately noticeable. Even the teachers who dispensed this unrealistic, out-of-date advice never used “shall” that way. So, what’s correct?
In my opinion, the answer can best be summed up with one simple rule: don’t use “shall” at all. Forget about it. You don’t need it. “Will” is used with all three persons: “I will…,” “you will…,” “we will…,” “they will…,” and so forth. “Shall” seems obsolete now, even anachronistic. It was outmoded in my childhood, and that’s a long time ago. (Never mind how long, exactly.) Nobody uses “shall” anymore, so, with two minor exceptions, forget about it.
There are still two situations where “shall” is used properly. First is the case where a futuristic question is being asked, mostly in the first person. For example, “Shall I choose one?” Or, “Shall we go now?” Using “will” here is awkward and changes the meaning of the sentence. “Will I choose one?” seems more to be asking a question, rather than stating something that will happen in the near future.
A second situation where “shall” is used is when a speaker wants to emphasize a point he’s trying to make. It’s a way of forcefully indicating a future event, as in the well-known phrase, “I shall return.” General MacArthur got it right when he left the Philippine Islands in 1942, after Japan had taken over most of that nation and was about to capture him. He wanted to emphasize that he’d be back. He did, too.
I went through the two sci-fi novels I’ve finished and looked for uses of the word “shall.” In the first novel, I found “shall” only twice. Once was where a somewhat pompous person was talking. That’s the way he talked, even though no one else in the novel talked like that. The second time was the futuristic question above, “Shall I choose one?” In my second novel, I found “shall” four times, all used by aliens who were talking poor English. None of the main characters used “shall.”
I suspect “shall” will stick around for a long time, probably because it’s used only in those two rare situations. Otherwise, it’s gone.