Shall and Will

“Shall” and “will” are modal verbs: they must combine with a verb to form a complete sentence.  Consider the following two examples:

1)      They shall forever.

2)      She will tomorrow.

These sentences are incomplete.  What shall they do forever?  What will she do tomorrow? 

When combined with a verb, both “shall” and “will” can indicate the time of an action, here “to live” and “to call”:

3)      They shall live forever.

4)      She will call tomorrow.

Here, “shall” and “will” indicate a future action.  Apart from indicating a future time of an action, they can indicate the stance of the speaker: “shall” and “will” can indicate how the speaker feels about the actions.  The Cambridge Grammar of the English Language points out that the common explanation of the difference between “shall” and “will” is not valid:

Expression of future

Person	Singular		Plural
First	I	shall	We	shall
Second	You	will	You	will
Third	He/She/It	will	They	will

Expression of will or determination

Person	Singular		Plural
First	I	will	We	will
Second	You	shall	You	shall
Third	He/She/It	shall	They	shall

If this prescriptive rule is not valid, how do you know which modal to use?

Common usage seems to be the best rule.  The Longman Grammar of Spoken and Written English states that “shall” appears much less frequently in both academic writing and conversation than does “will.”  Many style guides suggest that “shall” can sound more formal, may have specialized meaning (as in legal documents), and might seem more polite when asking consent in the first person (“Shall we dance?”) or even archaic (as in the King James Bible’s Ten Commandments “Thou shalt not kill”). 

“Will” is appropriate for most situations today.

Resources

As you can see from the following links, opinion is not clear on the difference: Grammar Girl and Rutgers. 

The following print resources are quite good.  Fowler offers a simple explanation.  Biber and Huddleston explore modals in depth

Biber, Douglas, Stig Johansson, Geoffrey Leech, Susan Conrad, and Edward Finegan.  Longman Grammar of Spoken and Written English.  Harlow:  Pearson, 1999.  Print.

Fowler, H. Ramsey, and Jane E. Aaron.  The Little, Brown Handbook.  8^th ed.  New York:  Longman, 2001.  Print.

Huddleston, Rodney, and Geoffrey K. Pullman.  The Cambridge Grammar of the English Language.  Cambridge:  CUP, 2002.  Print.