may/might

[P2052 at AOL.COM]

According to sources cited in Celce-Murcia's and Larsen-Freeman's helpful
work, The Grammar Book (1983), modals can be used in two different senses:
1) a root, or social interactional , one and 2) an epistemic, or logical[ly]
probab[le], one.  While some modals can be rendered in both ways, others
yield just one.

It is the first sense in which the modal, "may," indicates permission (i.e.
"May I go?"  "Yes, you may go.")    While "might" can render this root sense
in an interrogative sentence ("Might I assist you?"), it is not used in this
same sense in a declarative sentence (Yes, you might.")   While "Might I
assist you" is a request for permission to help, "Yes, you might" is an
inappropriate response since the root or social interactional sense is
replaced by an epistemic one.  Thus, "Yes, you might" indicates not
permission, but the possibility that the speaker might assist.  Consequently,
in response to the question, "Might I assist you?" the reply is usually,
"Yes, you may," the same one used to answer the question, "May I assist you?"


As for the epistemic or logical probability uses of both "may" and "might,"
one might find, "That may/might be true"  In this sense either modal can be
used; likewise, other modals are used as well, with the user's choice being
based on the degree of certainty of the action indicated by the lexical verb.

This information may/might or may/might not help you understand the
difference between these two modals.  If you find that it does not, you may (=
You have my permission to) disregard it..  If, on the other hand, you find it
useful, you may/might
(It is logically possible) consider checking the source (for a more detailed
discussion of modals).
                PAT                                     .