Two types of logical consequence are compared: one, with respect to matrix and designated elements and the other with respect to ordering in a suitable algebraic structure. Particular emphasis is laid on algebraic structures in which there is no top-element relative to the ordering. The significance of this special condition is discussed. Sequent calculi for a number of such structures are developed. As a consequence it is re-established that the notion of truth as such, not to speak of tautologies, is (...) inessential in order to define validity of an argument. (shrink)

In this paper, we will explore two initiatives that focus on the importance of employing logical theories in educating people how to think and reason properly, one in Poland: The Lvov-Warsaw School; the other in North America: The Informal Logic Initiative. These two movements differ in the logical means and skills that they focus on. However, we believe that they share a common purpose: to educate students in logic and reasoning (logical education conceived as a process) so that they may (...) be able to apply their skills to analyze the issues in their society (logical culture as a result of logical education). The aim of the paper is to justify this claim by exploring research objectives and products that are common to both movements. (shrink)

This essay attempts to give definitions and identity conditions for the two predominant senses of ‘Argument’ currently in use, the one involving reasons for a conclusion and the other denoting an expressed disagreement with ensuing verbal behaviour by two parties. I see Johnson's new concept of ‘Argument’, as developed in his book Manifest Rationality, as a hybrid of the two common senses of ‘Argument’, and, accordingly, I try to define and give the identity conditions of Johnson-arguments. Finally, I disagree with (...) Johnson on the nature of the definition he thinks he has proposed, and I conclude with observations suggesting that his logical perspective has dialectical and rhetorical components. (shrink)

This paper presents a unified, more-or-less complete, and largely pragmatic theory of indicative conditionals as they occur in natural language, which is entirely truth-functional and does not involve probability. It includes material implication as a special—and the most important—case, but not as the only case. The theory of conditional elements, as we term it, treats if-statements analogously to the more familiar and less controversial other truth-functional compounds, such as conjunction and disjunction.

Natural deduction is the type of logic most familiar to current philosophers, and indeed is all that many modern philosophers know about logic. Yet natural deduction is a fairly recent innovation in logic, dating from Gentzen and Jaśkowski in 1934. This article traces the development of natural deduction from the view that these founders embraced to the widespread acceptance of the method in the 1960s. I focus especially on the different choices made by writers of elementary textbooks—the standard conduits of (...) the method to a generation of philosophers—with an eye to determining what the ‘essential characteristics’ of natural deduction are. (shrink)

To prove the equivalence one must start with one side, and the earlier-later side seems, for starting with, logically the clearer. The equivalence is provable on reasonable definitions of ‘past’, ‘present’ and ‘future’ in terms of the earlier-later structure of time. McTaggart's attempted distinction between the past-present-future A series and the earlier-later B series, as though they were rivals for the structure of time, is based on an unexamined, and false, assumption. The equivalence shows they are not rivals; they are (...) quite consistent with each other. A very serious consequence is that all subsequent argument, from the A side or the B, however sophisticated, is flawed to the extent that it accepts McTaggart's false distinction. (shrink)

The object of this paper is to show why recent research in the psychology of deductive and probabilistic reasoning does not have.

The rhetoric-analytic critique of experimental psychology owes its apparent attractiveness to (a) some erroneous ideas about cognitive psychology and the rationale of experimentation, (b) the failure to distinguish between prior data and evidential data vis-à-vis the to-be-corroborated explanatory theory, and (c) evidential data owes their identity to a theory that is independent of the theory being tested. Theories in cognitive psychology are accepted because they can withstand concerted efforts to falsify them.

Routley?s Formula says, for instance, that if it is believed there is a man then there is something which is believed to be a man. In this paper I defend the formula; first directly, but then by looking at work by Gensler and Hintikka against it, and at the original work of Routley, Meyer and Goddard for it. The argument ultimately reduces to a central point about the extensionality of objects in Routley, Meyer and Goddard?s intensional system, i.e. in its (...) formulation of transparency. (shrink)

This work studies manipulative use of language that can be called “deliberate failure of communication”; I characterize this kind of manipulation and show that it can be found in the discourse of marketing experts and legal professionals. Relying on relevance theory, I show that manipulation of this kind takes advantage of what van Dijk calls the “context model” of the addressees. I exemplify two ways in which the context models of some of the discourse’s participants might be misused in order (...) to manipulate them. One way is exemplified by a text from an advertisement, the other by a text from a criminal court file. I propose, finally, that the analysis supports van Dijk’s view that social, discursive, and epistemic inequalities reproduce one another in a kind of vicious circle. It suggests, in van Dijk’s terms, that manipulation by deliberate failure of communication is a discriminatory use of language employed by elite groups in order to reproduce their social power. (shrink)

I will suggest, in this article, a possible explanation of the fact that legal language appears incoherent to the general public. I will present one legal text (an indictment), explaining why it appears incoherent to legal laypersons. I will argue that the traits making this particular text appear incoherent are, first, that a specialized legal meaning is conveyed implicitly and, second, that there are no key-words that could direct laypersons to the knowledge making this meaning obvious to legalists. I will (...) conclude that any legal text having these traits is likely to appear incoherent to the general public and suggest that the traits making my example appear incoherent might be rather common among the various texts of the various legal systems. On this suggestion there is no need to assume any causal relation between lawyers’ social interests and the apparent incoherence of legal language as it entails that this incoherence is inevitable. (I will argue that it is a result of the facts that legal language is ordinary language used, in the ordinary way, in the special context of the legal discourse.). (shrink)

En este estudio analizamos dos tendencias claramente distintas y contrapuestas en la forma de impartir cursos elementales de Lógica en la formación superior. Para este propósito, se ha seleccionado una muestra de manuales angloamericanos clásicos, así como otra más pequeña de la tradición iberoamericana para comprobar nuestras hipótesis. Los estilos identificados y analizados en dichos manuales son lo que hemos denominado lógica matemática y lógica para filósofos. En ambos casos se trata de tendencias muy generales reconocibles en las más diversas (...) tradiciones locales. El periodo analizado, 1940-1980, responde al proceso de introducción de la Lógica contemporánea en el ámbito académico occidental. (shrink)