The primary units of meaning in the use and comprehension of language are speech acts of the type called illocutionary acts. In Foundations of Illocutionary Logic John Searle and Daniel Vanderveken presented the first formalised logic of a general theory of speech acts. In Meaning and Speech Acts Daniel Vanderveken further develops the logic of speech acts and the logic of propositions to construct a general semantic theory of natural languages. Volume I, Principles of Language Use, explains the general principles that connect meaning, reason, thought and speech acts in the semantic structure of language. It presupposes no detailed knowledge of logical formalism, and will be accessible to a large readership of students and scholars from philosophy, linguistics, cognitive psychology and computer science. Volume II, Formal Semantics of Success and Satisfaction, uses the resources of philosophical and mathematical logics to develop a formalisation of the laws of the semantic theory advanced in Volume I. It will be of interest to theoretical linguists and those involved in mathematical logic and artificial intelligence.