The Commens Dictionary

Quote from ‘Graphs, Little Account [R]’

…if one person is to convey any information to another, it must be upon the basis of a common experience. They must not only have this common experience, but each must know the other has it; and not only that but each must know the other knows that he knows the other has it; so that when one says ‘It is cold’ the other may know that he does not mean that it is cold in Iceland or in Laputa, but right here. In short it must be thoroughly understood between them that they are talking about objects of a collection with which both have some familiarity. The collection of objects to which it is mutually understood that the propositions refer is called by exact logicians the universe of discourse.