Carnap, R. (1947). Meaning and necessity; a study in semantics and modal logic. University of Chicago Press.
A new method of symbolic logic for analyzing and describing the meanings of linguistic expressions is developed. The traditional method of the name-relation which considers each expression as a name of a concrete or abstract entity leads to numerous difficulties. These difficulties can be avoided by the new method which takes an expression as possessing an extension and an intension. A new way of defining L-terms (for example, "L-true" means "logically true") is suggested. This new semantical method is applied to the theory of modalities, such as necessity, possibility, etc. (See also 16: 2755.) (PsycINFO Database Record (c) 2016 APA, all rights reserved)