Jaakko Hintikka

Game-Theoretical Semantics

Game theory is a mathematical tool to study the behavior of independent agents in strategic interaction. Reasoning and communication have an essentially strategic aspect. Game theoretic is thus a suitable tool to illuminate the interactive aspects of logic and language.

Impossible Possible Worlds Vindicated

It has often been claimed that the by now familiar possible-two rids analysis of propositional attitudes like knowledge and belief which I have advocated since 1962 is unrealistic,1 if not downright mistaken, because it apparently commits us to the assumption of logical omniscience, that is, to the assumption that everyone knows all the logical consequences of what he knows, and analogously for all the other propositional attitudes. Since the assumption of such logical omniscience is obviously mistaken, this commitment seems to constitute a grave objection to the whole possible-worlds treatment of propositional attitudes.

Semantics for Propositional Attitudes

In the philosophy of logic a distinction is often made between the theory of reference and the theory of meaning.1 In this paper I shall suggest (inter alia) that this distinction, though not without substance, is profoundly misleading. The theory of reference is, I shall argue, the theory of meaning for certain simple types of language. The only entities needed in the so-called theory of meaning are, in many interesting cases and perhaps even in all cases, merely what is required in order for the expressions of our language to be able to refer in certain more complicated situations. Instead of the theory of reference and the theory of meaning we perhaps ought to speak in some cases of the theory of simple and of multiple reference, respectively. Quine has regretted that the term ‘semantics’, which etymologically ought to refer to the theory of meaning, has come to mean the theory of reference.1 I submit that this usage is happier than Quine thinks, and that large parts of the theory of meaning in reality are — or ought to be — but semantical theories for notions transcending the range of certain elementary types of concepts.

What is Abduction? The Fundamental Problem of Contemporary Epistemology

It is sometimes said that the highest philosophical gift is to invent important new philosophical problems. If so, Peirce is a major star on the firmament of philosophy. By thrusting the notion of abduction to the forefront of philosophers’ consciousness he created a problem which — I will argue — is the central one in contemporary epistemology.

The Intentions of intentionality and other new models for modalities

1. Different Constructions in Terms of the Basic Epistemological Verbs: A Survey of Some Problems and Proposals.- 2. The Semantics of Modal Notions and the Indeterminacy of Ontology.- 3. Objects of Knowledge and Belief: Acquaintances and Public Figures.- 4. Information, Causality, and the Logic of Perception.- 5. Carnaps Heritage in Logical Semantics.- 6. Quine on Quantifying in: A Dialogue.- 7. Answers to Questions.- 8. Grammar and Logic: Some Borderline Problems.- 9. Knowledge, Belief, and Logical Consequence.- 10. The Intentions of Intentionality.- 11. Concept as Vision: On the Problem of Representation in Modern Art and in Modern Philosophy.- Index of Names.- Index of Subjects.

Information and inference

I. Information and Induction.- On Semantic Information.- Bayesian Information Usage.- Experimentation as Communication with Nature.- II. Information and Some Problems of the Scientific Method.- On the Information Provided by Observations.- Quantitative Tools for Evaluating Scientific Systematizations.- Qualitative Information and Entropy Structures.- III. Information and Learning.- Learning and the Structure of Information.- IV. New Applications of Information Concepts.- Surface Information and Depth Information.- Towards a General Theory of Auxiliary Concepts and Definability in First-Order Theories.- Index of Names.- Index of Subjects.

Interrogative Logic as a General Theory of Reasoning

Publisher Summary This chapter focuses on interrogative logic as a general theory of reasoning. The interrogative method is the theory of reasoning, logical along with the empirical, comprising deductive logic as a special case. The interrogative approach can be argued to be a general theory of reasoning. There are two kinds of moves, logical inference moves and interrogative moves. The logical inference moves are simply a variant of the tableau building rules of the usual tableau method. For simplicity, the chapter assumes that all the formulas the chapter deals with are in the negation normal form, that is, that all negation signs precede immediately atomic formulas or identities, unless otherwise indicated. The basic concepts of the tableau method, such as column, closure and subtableau, are used as usual. In order to obtain a more concise notation the chapter formulates the tableau building rules as inverses of the corresponding Genzen-style (sequent) rules.

A Two-Dimensional Continuum of Inductive Methods*

Publisher Summary This chapter compares a number of inductive methods with each other. All these different systems are fitted into one and the same continuum of inductive methods. The members of this continuum are characterized by two parameters, such as λ and α. A new parameter α is comparable with Carnaps old λ that is also an index of the weight of the a priori (logical) factor in induction. Of these, λ is essentially the same as its namesake in Carnaps λ-continuum. The only difference between the two parameters is that they pertain to different kinds of inductive inferences: α is relevant to inductive generalization, whereas λ pertains to the singular predictive inference, more generally, to an inference from particulars to particulars. The main novelty here, as compared with Carnaps systems, is that most generalizations (closed sentences) that are not logically true receive asymptotically well-behaved degrees of confirmation (different from zero) in an infinite universe.

The Varieties of Information and Scientific Explanation

The concept of information seems to be strangely neglected by epistemologists and philosophers of language. In many everyday situations, knowledge and information are nearly exchangeable terms; yet for every score of books with the phrase “theory of knowledge” in their titles there scarcely exists a single paper by a logician or philosopher dealing with the theory of information.1 Again, the information that a sentence yields or can yield might very well seem to an ordinary man much more important than the so-called meanings of the terms it contains, or even the meaning of the sentence itself. Yet, with but few exceptions, philosophers of language have not devoted more than a vanishingly small part of their efforts to the theory of information as compared with the theory of meaning. Why this should be so, I do not know. Perhaps the fact that mathematicians and communication theorists largely succeeded in appropriating the term “information” for their special purposes a couple of decades ago has something to do with this.2 I also suspect that it is much harder to talk persuasive nonsense about the quantitative concept of information than of the qualitative notions of knowledge and meaning. Be this as it may, the neglect is a regrettable one. In this paper, I shall try to call philosophers’ attention to a few possibilities of correcting it. I have already tried to do so in some earlier papers 3; the present one is partly a sequel to them and partly a new enterprise.

Chapter 6 – Game-Theoretical Semantics

Publisher Summary The leading ideas of game-theoretical semantics (GTS) can be seen best from a special case of the semantics of quantifiers. In using quantifiers and in theorizing about them, it is hard not to use game-laden terms. This chapter focuses on the game-theoretical semantics (GTS). The game-theoretical interpretation for the ordinary first-order languages is extended to cover also the sentences of the new language. The game rules for the new language is the same as the old ones. The only essential difference between the new and the old games is, thus, that the former are the games of imperfect information. The resulting logic is called “independence friendly (IF) first-order logic” and the languages associated with it are IF first-order languages. GTS is only one of the possible semantical treatments of first-order logic.