universe of discourse

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A class containing all the entities referred to in a discourse or argument.

from the GNU version of the Collaborative International Dictionary of English.

• noun everything which may be considered, explicitly or implicitly, in a particular theory or discussion.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun logic The set of all entities over which quantifiers—including "for all" and "there exists"—range.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun everything stated or assumed in a given discussion