This presentation of a system of propositional logic is a foundational paper for systems of illocutionary logic. The language contains the illocutionary force operators '' for assertion and ' ' for supposition. Sentences occurring in proofs of the deductive system must be prefixed with one of these operators, and rules of take account of the forces of the sentences. Two kinds of semantic conditions are investigated; familiar truth conditions and commitment conditions. Accepting a statement A or rejecting A commits a (...) person to accepting some statements (the symbol '' marks this value), to rejecting some statements (), and will leave the person uncommitted with respect to others (). Commitment valuations assign the values to sentences of ; such a valuation is conceived as reflecting the beliefs/knowledge of a particular person. This paper explores the relations between truth conditions and commitment conditions, and between semantic concepts defined in terms of these conditions. (shrink)

This paper uses the resources of illocutionary logic to provide a new understanding of the Liar Paradox. In the system of illocutionary logic of the paper, denials are irreducible counterparts of assertions; denial does not in every case amount to the same as the assertion of the negation of the statement that is denied. Both a Liar statement, (a) Statement (a) is not true, and the statement which it negates can correctly be denied; neither can correctly be asserted. A Liar (...) statement, more precisely, an attempted Liar statement, fails to fulfill conditions essential to statements, but no linguistic rules are violated by the attempt. Ordinary language, our ordinary practice of using language, is not inconsistent or incoherent because of the Liar. We are committed to deny Liars, but not to accept or assert them. This understanding of the Liar Paradox and its sources cannot be fully accommodated in a conventional logical system, which fails to mark the distinction between sentences/statements and illocutionary acts of accepting, rejecting, and supposing statements. (shrink)

This paper further develops the system of illocutionary logic presented in ?Propositional logic of supposition and assertion? (Notre Dame Journal of Formal Logic 1997, 38, 325-349) to accommodate an ?I believe that? operator and resolve Moore's Paradox. This resolution is accomplished by providing both a truth-conditional and a commitment-based semantics. An important feature of the logical system is that the correctness of some arguments depends on who it is that makes the argument. The paper then shows that the logical system (...) can be expanded to resolve the surprise execution paradox puzzle. The prisoner's argument showing that he can't be executed by surprise is correct but his beliefs are incoherent. The judge's beliefs (and our beliefs) about this situation are not incoherent. (shrink)

This paper explores Church's Thesis and related claims madeby Turing. Church's Thesis concerns computable numerical functions, whileTuring's claims concern both procedures for manipulating uninterpreted marksand machines that generate the results that these procedures would yield. Itis argued that Turing's claims are true, and that they support (the truth of)Church's Thesis. It is further argued that the truth of Turing's and Church'sTheses has no interesting consequences for human cognition or cognitiveabilities. The Theses don't even mean that computers can do as much (...) as peoplecan when it comes to carrying out effective procedures. For carrying out aprocedure is a purposive, intentional activity. No actual machine does, orcan do, as much. (shrink)

In this paper, I present a modified and extended version of combinatory logic. Schönfinkel originated the study of combinatory logic (in [2]), but its development is primarily due to H. B. Curry. In the present paper, I will make use of both the symbolism (with some modification) and the results of Curry, as found in [1].What is novel about my version of combinatory logic is a kind of combinators which I call discriminators. These combinators discriminate between different symbols, and yield (...) values which are determined by the symbols which are their arguments. If the normal combinators investigated by Curry are considered as functions taking (combinations of) symbols as arguments and yielding symbols as values, these combinators can rearrange and cancel their arguments or introduce new symbols. (shrink)

Presents a new framework for understanding language, thought, and experience, and for carrying out research.

Clear focus on its application of formal logic to ordinary English is the most distinctive feature of this textbook for the introductory course in deductive logic. Great care is taken with the appropriate translation into logical languages of ordinary English sentences. Evaluation of these translations promotes a more effective use of ordinary language. The Principles of Deductive Logic presents symbolic logic in a fuller and more leisurely fashion than other introductory textbooks. Early chapters cover informal material, including definition and informal (...) fallacies. The remainder of the text is devoted to the treatment of four distinct artificial languages. The Categorical language is the language of syllogistic logic. The Extended Categorical language enriches this first language with the symbolic connectives for conjunction and negation. The Propositional Connective language and the First-Order language are the two basic languages of modern logic. Each language is accompanied by a deductive system, and is used as an instrument for exploring ordinary language, including ordinary arguments The book contains a large number of exercises whose answers are supplied in the back of the book, and many more that can be assigned as homework. A solution’s manual is available to instructors upon their request. The request must be written on college or university letterhead. (shrink)

I distinguish a priori knowledge from a priori truths or statements. A priori knowledge either is evident or is derived from evident premisses by means of correct reasoning. An a priori statement is one that reflects features of the conceptual framework within which it is placed. The statement either describes semantic relations between concepts of the framework or it characterizes the application of the framework to experience and the world. An a priori statement is not necessarily part of anyone’s a (...) priori knowledge. I also distinguish empirical knowledge from empirical statements. Both statements and theories are empirical if they are designed to characterize features of experience and the world. Knowledge is empirical if it fits experience; thus, one must check to see whether it fits. We do not obtain knowledge of logical systems by rational insight of evident truths and careful deductions from evident truths. Adequate logical systems are developed by trial and error. Logical knowledge is empirical knowledge that is not generally a priori. It is empirical knowledge of a priori truths and principles of our conceptual systems. Logical systems are empirical theories of these truths and principles. (shrink)

This paper is an introduction to illocutionary logic, i.e. the logic of speech acts. The author proposes an approach to this subject matter that is different from John Searle’s and Daniel Vanderveken’s views. They conceive illocutionary logic as a supplement or an appendix to standard logic, pro..

This paper explores Church's Thesis and related claims madeby Turing. Church's Thesis concerns computable numerical functions, whileTuring's claims concern both procedures for manipulating uninterpreted marksand machines that generate the results that these procedures would yield. Itis argued that Turing's claims are true, and that they support (the truth of)Church's Thesis. It is further argued that the truth of Turing's and Church'sTheses has no interesting consequences for human cognition or cognitiveabilities. The Theses don't even mean that computers can do as much (...) as peoplecan when it comes to carrying out effective procedures. For carrying out aprocedure is a purposive, intentional activity. No actual machine does, orcan do, as much. (shrink)