Both “shall” and “will” indicate a future action, but there are some subtleties that have to do with modality, which I shall discuss today.
In the first person (I or we), “shall” is used for future tense. In second and third persons (you, he, she, they), “shall” indicates a command or prophecy modality.
First Person Examples:
I shall go to the budget meeting tomorrow.
Shall we play golf this Saturday?
We shall overcome.
Second Person Example (command):
Bob, you shall go to the budget meeting tomorrow, no matter how much work you have!
You shall not steal. You shall not bear false witness.
Third Person Example:
According to the Mayan calendar, the end of the world shall come in 2012.
The converse of the “shall” rule is true for “will.”
“Will” indicates the modality of willingness or determination in the first person, whereas “will” indicates future tense in the second and third persons.
I will lose ten pounds before my class reunion. (first person determination)
You will learn how to drill a horizontal well in this class. (second person future)
The contractor will install the steam generator tomorrow morning. (third person future)
“Shall” is also used in regulations and engineering specifications.
– Diesel trucks exceeding these particulate emissions limits shall be fined $20,000.
– The control valve shall be able to operate within specifications up to 130°F.
In both cases, shall is used in the third person to express determination or command.