Besides pure declarative arguments, whose premises and conclusions are declaratives, and pure imperative arguments, whose premises and conclusions are imperatives, there are mixed-premise arguments, whose premises include both imperatives and declaratives, and cross-species arguments, whose premises are declaratives and whose conclusions are imperatives or vice versa. I propose a general definition of argument validity: an argument is valid exactly if, necessarily, every fact that sustains its premises also sustains its conclusion, where a fact sustains an imperative exactly if it favors (...) the satisfaction over the violation proposition of the imperative, and a fact sustains a declarative exactly if, necessarily, the declarative is true if the fact exists. I argue that this definition yields as special cases the standard definition of validity for pure declarative arguments and my previously defended definition of validity for pure imperative arguments, and that it yields intuitively acceptable results for mixed-premise and cross-species arguments. (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)

Besides pure declarative arguments, whose premises and conclusions are declaratives (“you sinned shamelessly; so you sinned”), and pure imperative arguments, whose premises and conclusions are imperatives (“repent quickly; so repent”), there are mixed-premise arguments, whose premises include both imperatives and declaratives (“if you sinned, repent; you sinned; so repent”), and cross-species arguments, whose premises are declaratives and whose conclusions are imperatives (“you must repent; so repent”) or vice versa (“repent; so you can repent”). I propose a general definition of argument (...) validity: an argument is valid exactly if, necessarily, every fact that sustains its premises also sustains its conclusion, where a fact sustains an imperative exactly if it favors the satisfaction over the violation of the imperative, and a fact sustains a declarative exactly if, necessarily, the declarative is true if the fact exists. I argue that this definition yields as special cases the standard definition of validity for pure declarative arguments and my previously defended definition of validity for pure imperative arguments, and that it yields intuitively acceptable results for mixed-premise and cross-species arguments. (shrink)

Now in a new edition, this volume updates Davidson's exceptional Inquiries into Truth and Interpretation (1984), which set out his enormously influential philosophy of language. The original volume remains a central point of reference, and a focus of controversy, with its impact extending into linguistic theory, philosophy of mind, and epistemology. Addressing a central question--what it is for words to mean what they do--and featuring a previously uncollected, additional essay, this work will appeal to a wide audience of philosophers, linguists, (...) and psychologists. (shrink)

Herbert G. Bohnert (1918–84) was a student and lifelong friend of Carnap. He wrote a doctoral thesis on Ramsey sentences and, after wavering between academia and the computer industry, eventually taught at Michigan State University. Bohnert defended Carnapian positions throughout his career and was especially productive in the 1970s. Unfortunately, Carnap’s philosophy was deemed hopelessly out of date during this period, and partly for this reason, Bohnert is almost completely forgotten today. This fate is undeserved. In this article, I reconstruct (...) his career and philosophical development by drawing on publications, as well as diary entries and private correspondence. I then argue that Carnap scholarship would benefit from closer attention to Bohnert’s writings. I support this claim by means of a case study from the philosophy of mathematics: Bohnert’s account of a conversation about set theory with Carnap in 1968 sheds new light on the contested question of whether Carnap held mathematics to be analytic in natural language. (shrink)

Formalising deontic concepts, such as obligation, prohibition and permission, is normally carried out in a modal logic with a possible world semantics, in which some worlds are better than others. The main focus in these logics is on inferring logical consequences, for example inferring that the obligation O q is a logical consequence of the obligations O p and O. In this paper we propose a non-modal approach in which obligations are preferred ways of satisfying goals expressed in first-order logic. (...) To say that p is obligatory, but may be violated, resulting in a less than ideal situation s, means that the task is to satisfy the goal p ∨ s, and that models in which p is true are preferred to models in which s is true. Whereas, in modal logic, the preference relation between possible worlds is part of the semantics of the logic, in this non-modal approach, the preference relation between first-order models is external to the logic. Although our main focus is on satisfying goals, we also formulate a notion of logical consequence, which is comparable to the notion of logical consequence in modal deontic logic. In this formalisation, an obligation O p is a logical consequence of goals G, when p is true in all best models of G. We show how this non-modal approach to the treatment of deontic concepts deals with problems of contrary-to-duty obligations and normative conflicts, and argue that the approach is useful for many other applications, including abductive explanations, defeasible reasoning, combinatorial optimisation, and reactive systems of the production system variety. (shrink)

In a recent paper, Sven Danielsson argued that the ‘original paradoxes' of deontic logic, in particular Ross's paradox and Prior's paradox of derived obligation, can be solved by restricting the modal inheritance rule. I argue that this does not solve the paradoxes.

In recent years philosophers have given a good deal of attention to imperatives. They have concerned themselves mainly with the logical grammar of sentences of this kind, that is to say their relations to each other and to interrogative and indicative sentences. Very often this topic has been raised in terms of the problem ‘Is imperative inference possible, and if so, what kind of inference is it?’. Many philosophers have contended that there are logically valid inferences that involve imperative sentences. (...) Against this it has been argued that no such inferences are possible. It has even been held that there are no such things as imperatives at all – regarded, that is, as types of expression logically sui generis and independent of indicative sentences. (shrink)

In recent years philosophers have given a good deal of attention to imperatives. They have concerned themselves mainly with the logical grammar of sentences of this kind, that is to say their relations to each other and to interrogative and indicative sentences. Very often this topic has been raised in terms of the problem ‘Is imperative inference possible, and if so, what kind of inference is it?’. Many philosophers have contended that there are logically valid inferences that involve imperative sentences. (...) Against this it has been argued that no such inferences are possible. It has even been held that there are no such things as imperatives at all – regarded, that is, as types of expression logically sui generis and independent of indicative sentences. (shrink)

In 1926, Mally proposed the first formal deontic system. As Mally and others soon realized, this system had some rather strange consequences. We show that the strangeness of Mally's system is not so much due to Mally's informal deontic principles as to the fact that he formalized those principles in terms of the propositional calculus. If they are formalized in terms of relevant logic rather than classical logic, one obtains a system which is related to Anderson's relevant deontic logic and (...) not nearly as strange as Mally's own system. (shrink)

Drawing on the work of Jeremy Bentham, we can forward a parity thesis concerning formal and substantive legal invalidity. Formal and substantive invalidity are, according to this thesis, traceable to the same source, namely, the sovereign's inability to adjust expectations to motivate obedience. The parity thesis, if defensible, has great appeal for positivists. Explaining why contradictory or contrary mandates yield invalidity is unproblematic. But providing an account of content-based invalidity invites the collapse of the separation between what the law is (...) and what the law ought to be. Grounding formal and substantive invalidity in a unified source allows us to avoid bringing in any additional apparatus that might compromise this separation. This essay fleshes out and defends the parity thesis. (shrink)