This is a reply to @FitzE.
https://www.englishclub.com/grammar/verbs-modals_shall-will.htm
This explanation of will/shall (link provided by @OntheFnce) indicates there are two different conjugations of the verb “will”. For a simple, objective sense, one uses “shall” for I and we, and “will” otherwise.
However, this article says there is a second conjugation for a more emphatic emphasis, or command, in which case it reverses, with “will” used with I and we, and “shall” used otherwise.
So, one would say
“I shall be arriving in London by train.” (simple case)
“I will try my utmost to suppress the rebellion.” (emphatic case)
“You will be served in great luxury. (Simple)
“You shall stop posting on any legal matters. (Command)
I was not asking about the use of will/shall in legal
terminology, but in everyday speech or writing. However, the rule that one uses “shall” with he/she/you/they when using the emphatic or command mode explains why legal documents would say things like:
“Landlord shall give 30 days notice to end the tenancy.”
If not using the “command” form of the verb, the document would need to say, “The landlord is obligated to give …”.
The conjugations also carry over to would/should, and the article noted that when asking for a catalogue, the proper phrasing is:
“I should be grateful if you would be so kind as to send me a copy of your most recent catalogue.
Other stuff I’ve read says that, aside from use in legal documents in the command form, “shall” survives mostly as a part of an invitation:
Shall I call a taxi?
Shall we dance?
Or, as KM used it, “Shall I post…”
The discussion of shall/will is, to me, by far the most interesting thing discussed in these threads in days.