The volume analyses and develops David Makinson’s efforts to make classical logic useful outside its most obvious application areas. The book contains chapters that analyse, appraise, or reshape Makinson’s work and chapters that develop themes emerging from his contributions. These are grouped into major areas to which Makinsons has made highly influential contributions and the volume in its entirety is divided into four sections, each devoted to a particular area of logic: belief change, uncertain reasoning, normative systems and the resources (...) of classical logic. Among the contributions included in the volume, one chapter focuses on the “inferential preferential method”, i.e. the combined use of classical logic and mechanisms of preference and choice and provides examples from Makinson’s work in non-monotonic and defeasible reasoning and belief revision. One chapter offers a short autobiography by Makinson which details his discovery of modern logic, his travels across continents and reveals his intellectual encounters and inspirations. The chapter also contains an unusually explicit statement on his views on the role of logic in philosophy. (shrink)

The author distinguishes two concepts of practical reason: (a) practical reason as a source of practical principles, and (b) practical reason as the theory of thought operations connected with action. He proves that there is no practical recognition in the sense (a). We can deal with actions only on the basis of dichotomic semantics. Critical analyses of some theories of practical reason are presented (Kant, Lorenzen, Apel, Alexy). The critical part of the paper mainly concerns the discourse theory and its (...) implications for practical philosophy and jurisprudence. (shrink)

Imperatives cannot be true or false, so they are shunned by logicians. And yet imperatives can be combined by logical connectives: "kiss me and hug me" is the conjunction of "kiss me" with "hug me". This example may suggest that declarative and imperative logic are isomorphic: just as the conjunction of two declaratives is true exactly if both conjuncts are true, the conjunction of two imperatives is satisfied exactly if both conjuncts are satisfied—what more is there to say? Much more, (...) I argue. "If you love me, kiss me", a conditional imperative, mixes a declarative antecedent ("you love me") with an imperative consequent ("kiss me"); it is satisfied if you love and kiss me, violated if you love but don't kiss me, and avoided if you don't love me. So we need a logic of three -valued imperatives which mixes declaratives with imperatives. I develop such a logic. (shrink)

The author investigates how the conception of legal validity as a specific mode of existence, adopted by Kelsen in Allgemeine Theorie der Normen (General Theory of Norms), can be reconciled with a conception of the legal system in which conflicts of legal norms remain of logical concern. To this end he makes use of Ludwig Wittgenstein's picture theory of the proposition as set out in the Tractatus Logico-Philosophicus. The conclusion is that in order to reconcile the two conceptions, the legal (...) system itself must be conceived of as consisting of three sub-systems, namely, (i) a sub-system of perceptible legal judgments, (ii) a sub-system of valid legal conditions, and (iii) a sub-system of observable social practices. (shrink)

Modern belief revision theory is based to a large extent on partial meet contraction that was introduced in the seminal article by Carlos Alchourrón, Peter Gärdenfors, and David Makinson that appeared in 1985. In the same year, Alchourrón and Makinson published a significantly different approach to the same problem, called safe contraction. Since then, safe contraction has received much less attention than partial meet contraction. The present paper summarizes the current state of knowledge on safe contraction, provides some new results (...) and offers a list of unsolved problems that are in need of investigation. (shrink)