Hans Rott

The paper suggests a way of viewing the two Fregean principles of compositionality and contextuality as working together in the enterprise of interpretation. A third Fregean theme, that of elucidation (more precisely, the elucidation of primitive, undefinable terms of logic, mathematics and metamathematics) secures a place for some version of the context principle in Frege's later writings. When thinking about the functioning of elucidations, Frege acknowledges a principle of charitable interpretation. I argue that there is a deep connection between the three themes, and that not only compositionality and contextuality, but also charity is a genuinely Fregean theme. Context. Interpretation. Linguistics. Logic. Meaning. Word.

This paper investigates the formal relationship between two prominent approaches to the logic of belief change. The first one uses the idea of "relational partial meet contractions" as developed by Alchourrón, Gärdenfors and Makinson (Journal of Symbolic Logic 1985), the second one uses the concept of "epistemic entrenchment" as elaborated by Gärdenfors and Makinson (in Theoretical Aspects of Reasoning about Knowledge, M. Y. Vardi, Los Altos 1988). The two approaches are shown to be strictly equivalent via direct links between the underlying formal relations. The paper closes with observations about the application of epistemic entrenchment to simple and iterated revisions.

Using Gärdenfors's notion of epistemic entrenchment, we develop the semantics of a logic which accounts for the following points. It explains why we may generally infer `If ~A then B´ if all we know is AvB while must not generally infer `If ~A then B´ if all we know is {AvB, A}. More generally, it explains the nonmonotonic nature of the consequence relation governing languages which contain conditionals, and it explains how we can deduce conditionals from premise sets without conditionals. Depending on the language at hand, our logic provides different ways of keeping the Ramsey test and getting round the Gärdenfors triviality theorem. I argue that consistent additions of new items of belief are not to be performed by transitions to logical expansions.

This paper is about the statics and dynamics of belief states that are represented by pairs consisting of an agent's credences (represented by a subjective probability measure) and her categorical beliefs (represented by a set of possible worlds). Regarding the static side, we argue that the latter proposition should be coherent with respect to the probability measure and that its probability should reach a certain threshold value. On the dynamic side, we advocate Jeffrey conditionalisation as the principal mode of changing one's belief state. This updating method fits the idea of the Lockean Thesis better than plain Bayesian conditionalisation, and it affords a flexible method for adding and withdrawing categorical beliefs. We show that it fails to satisfy the traditional principles of Inclusion and Preservation for belief revision and the principle of Recovery for belief withdrawals{, as well as the Levi and Harper identities. We take this to be a problem for the latter principles rather than for the idea of coherent belief change.

This paper explores conditionals expressing that the antecedent makes a difference for the consequent. A 'relevantised' version of the Ramsey Test for conditionals is employed in the context of the classical theory of belief revision. The idea of this test is that the antecedent is relevant to the consequent in the following sense: a conditional is accepted just in case (i) the consequent is accepted if the belief state is revised by the antecedent and (ii) the consequent fails to be accepted if the belief state is revised by the antecedent's negation. The connective thus defined violates almost all of the traditional principles of conditional logic, but it obeys an interesting logic of its own. The paper also gives the logic of an alternative version, the `Dependent Ramsey Test', according to which a conditional is accepted just in case (i) the consequent is accepted if the belief state is revised by the antecedent and (ii) it is rejected (e.g., its negation is accepted) if the belief state is revised by the antecedent's negation. This conditional is closely related to David Lewis's counterfactual analysis of causation.

This paper combines various structures representing degrees of belief, degrees of disbelief, and degrees of non-belief (degrees of expectations) into a unified whole. The representation uses relations of comparative necessity and possibility, as well as non-probabilistic functions assigning numerical values of necessity and possibility. We define all-encompassing necessity structures which have weak expectations (mere hypotheses, guesses, conjectures, etc.) occupying the lowest ranks and very strong, ineradicable ('a priori') beliefs occupying the highest ranks. Structurally, there are no differences from the top to the bottom. I argue that belief is a vague notion, and that thresholds for belief, if there are any, are context-dependent.

The classical qualitative theory of belief change due to Alchourrón, Gärdenfors and Makinson has been widely known as being characterised by two packages of postulates. While the basic package consists of six postulates and is very weak, the full package that adds two further postulates is very strong. I revisit two classic constructions of theory contraction, viz., relational possible worlds contraction and entrenchment-based contraction and argue that four intermediate levels can be distinguished that play - or ought to play - important roles within qualitative belief revision theory. Levels 3 and 4 encode two ways of interpreting the idea of imperfect discrimination of the plausibilities of possible worlds or propositions.

An idea going back to Plato’s Meno is that knowledge is stable. Recently, a seemingly stronger and more exciting thesis has been advanced, namely that rational belief is stable. I sketch two stability theories of knowledge and rational belief, and present an example intended to show that knowledge need not be stable and rational belief need not be stable either. The second claim does not follow from the first, even if we take knowledge to be a special kind of rational belief. ‘Stability’ is an ambiguous term that has an internally conditional structure.

Drawing inspiration from Lakatos’s philosophy of science, the paper presents a notion of intertheory explanation that is suitable to explain, from the point of view of a successor theory, its predecessor theory’s success (where it is successful) as well as the latter’s failure (where it fails) at the same time. A variation of the Ramsey-test is used, together with a standard AGM belief revision model, to give a semantics for open and counterfactual conditionals and ’because’-sentences featuring in such intertheory explanations. Pre-theoretically described idealizing assumptions play a crucial role in this model, especially when the predecessor theory and the successor theory contradict each other.

This paper studies the idea of conservatism with respect to belief change strategies in the setting of unary, iterated belief revision functions (based on the conclusions of Rott, ‘Coherence and Conservatism in the Dynamics of Belief, Part I: Finding the Right Framework’, Erkenntnis 50, 1999, 387–412). Special attention is paid to the case of ‘basic belief change’ where neither the (weak) AGM postulates concerning conservatism with respect to beliefs nor the (stong) supplementary AGM postulates concerning dispositional coherence need to be satisfied. One‐step belief change generated by ‘basic entrenchment’ is combined with a natural conservative method of revising entrenchment relations. A logical characterization of this method is presented, and it is compared with three other methods known from the literature which I call ‘external’, ‘radical’ and ‘moderate’ belief revision. While conservative belief change turns out to be incoherent in its treatment of the recency of information, moderate belief change is more satisfactory in this respect.

The paper aims at a perspicuous representation of Isaac Levi's pragmatist epistemology, spanning from the 1967 classic "Gambling with Truth" to his 2004 book on "Mild Contraction". Based on a formal framework for Levi's notion of inquiry, I analyse his decision-theoretic approach with truth and information as basic cognitive values, and with Shackle measures as emerging structures. Both cognitive values figure prominently in Levi's model of inductive belief expansion, but only the value of information is employed in his model of belief contraction. I argue that the former model is more successful than the latter.

The paper attacks the widely held view that belief revision theories, as they have been studied in the past two decades, are founded on the Principle of Informational Economy. The principle comes in two versions. According to the first, an agent should, when accepting a new piece of information, aim at a minimal change of his previously held beliefs. If there are different ways to effect the belief change, then the agent should, according to he second version, give up those beliefs that are least entrenched. Although widely proclaimed by belief revision theorists, I argue that both versions of the principle are dogmas that are not (and perhaps should not be) adhered to. I substantiate this claim with two simple mathematical observations, and I defend it against four possible objections that involve contractions, reconstructions, dispositions, and truths.

Descartes' Meditations do not end up sceptical at all. In fact, the sixth meditation displays an intriguing epistemological optimism. Descartes affirms without reservation that knowledge of the external world is possible. The antisceptical argument at the end of the Meditations is often interpreted as a refutation of dream scepticism, with the conclusion that a person in the waking state can also determine that he or she is awake. We examine the logic of the argument in detail and find that this is not the point. Our reconstruction shows that the question of waking or dreaming which seems to be so crucial for Descartes can even be dropped from his argument.

The paper attempts to reconcile two very different approaches to the concept of causation. In the original form, it is the opposition found in Laplace between his doctrine of constant and variable causes on the one hand and his mechanistic determinism on the other. This tension was described clearly only by Maxwell who stressed the contrast between the statistical and the dynamical method (calling the latter also the historical or strictly kinetic method). A similar dichotomy surfaces in the work of Wesley Salmon who distinguished statistical from aleatory causation. Acknowledging that we seem to have conflicting intuitions about causality and explanation, I argue that assigning probabilistic laws a fundamental role in scientific explanation does not conflict with the assumption of Laplacian determinism. This is due to the fact that in most systems of interest, we confront a complex interaction of multiple causal factors and an extreme sensitivity to small variations of initial conditions.

This article explores conditionals expressing that the antecedent makes a difference for the consequent. A ‘relevantised’ version of the Ramsey Test for conditionals is employed in the context of the classical theory of belief revision. The idea of this test is that the antecedent is relevant to the consequent in the following sense: a conditional is accepted just in case the consequent is accepted if the belief state is revised by the antecedent and the consequent fails to be accepted if the belief state is revised by the antecedent’s negation. The connective thus defined violates almost all of the traditional principles of conditional logic, but it obeys an interesting logic of its own. The article also gives the logic of an alternative version, the ‘Dependent Ramsey Test,’ according to which a conditional is accepted just in case the consequent is accepted if the belief state is revised by the antecedent and the consequent is rejected if the belief state is revised by the antecedent’s negation. This conditional is closely related to David Lewis’s counterfactual analysis of causation.

Prioritized bases, i.e., weakly ordered sets of sentences, have been used for specifying an agent’s ‘basic’ or ‘explicit’ beliefs, or alternatively for compactly encoding an agent’s belief state without the claim that the elements of a base are in any sense basic. This paper focuses on the second interpretation and shows how a shifting of priorities in prioritized bases can be used for a simple, constructive and intuitive way of representing a large variety of methods for the change of belief states—methods that have usually been characterized semantically by a system-of-spheres modeling. Among the methods represented are ‘radical’, ‘conservative’ and ‘moderate’ revision, ‘revision by comparison’ in its raising and lowering variants, as well as various constructions for belief expansion and contraction. Importantly, none of these methods makes any use of numbers.

This paper explores the connective ‘because’, based on the idea that ‘CbecauseA’ implies the acceptance/truth of the antecedentAas well as of the consequentC, and additionally that the antecedent makes a difference for the consequent. To capture this idea of difference-making a ‘relevantized’ version of the Ramsey Test for conditionals is employed that takes the antecedent to be relevant to the consequent in the following sense: a conditional is true/accepted in a state$$\sigma $$σjust in case (i) the consequent is true/accepted when$$\sigma $$σis revised by the antecedentand(ii) the consequent fails to be true/accepted when$$\sigma $$σis revised by the antecedent’s negation. To extend this to a semantics for ‘because’, we add that (iii) the antecedent and (iv) the consequent are accepted/true in the state$$\sigma $$σ. We get metaphysical or doxastic interpretations of these clauses, depending on what we mean by a model and a state. We introduce several semantics known from suppositional conditionals, which we reinterpret for difference-making conditionals and ‘because’. We present a minimal logic for ‘because’ sentences and show how it can be extended in ways that parallel the hierarchy of extensions of the logic of suppositional conditionals. We establish correspondence results between axioms for ‘because’ and properties of states, and prove that the specified logics are sound with respect to the semantics.

The concept of an evidential conditional If A then C that can be defined by the conjunction of A>C and ¬C>¬A, where > is a conditional of the kind introduced by Stalnaker and Lewis, has recently been studied in a series of papers by Vincenzo Crupi and Andrea Iacona. In this paper I argue that Crupi and Iacona’s central idea that contraposition captures the idea of evidential support cannot be maintained. I give examples showing that contraposition is neither necessary nor sufficient for a conditional’s antecedent supporting its consequent. Crupi and Iacona’s alternative account of evidential conditionals that is based on a probabilistic measure of evidential support cannot add to the credentials of their modal account, because both the theoretical role of contraposition and the resulting logic are different in this account.

This note presents a very brief history of the observation that the probability of the material conditional A⊃B is in general different from, but cannot be less than, the conditional probability of B given A. The difference between the two probabilities is significant for the interpretation of conditionals and for the possibility of inductive probability. It can be quantitatively specified in so-called ‘excess laws’ for which Popper appears to have claimed priority. I argue that such a priority claim should be rejected and credit should instead be given, if to anyone, to Boole and Reichenbach instead.

This is a survey paper. Contents: 1 Introduction -- 2 The representation of belief -- 3 Kinds of belief change -- 4 Coherence constraints for belief revision -- 5 Different modes of belief change -- 6 Two strategies for characterizing rational changes of belief - 6.1 The postulates strategy - 6.2 The constructive strategy -- 7 An abstract view of the elements of belief change -- 8 Iterated changes of belief -- 9 Further developments - 9.1 Variants and extensions of belief revision - 9.2 Updates - 9.3 Default inferences as expectation revision - 9.4 Belief merging -- 10 Concluding remarks

The dominant analyses of the logical form of natural-language conditionals take them to be “suppositional conditionals”. The latter are true or accepted if the consequent is true/accepted on the supposition of the antecedent. But this can happen although the antecedent is completely irrelevant (or even somewhat adverse) to the consequent. In natural-language conditionals, however, the antecedent is typically meant to support or be evidence for the consequent. The logical form of conditionals will thus be more complex than the suppositional theory would have it. Recently some suggestions as to what this logical form might look like have been made. In this paper, I critically discuss Vincenzo Crupi and Andrea Iacona’s account of “evidential conditionals”, including its recent amendments.

Dogmatic, naive and sophisticated falsificationism are construed as being distinguished by different views on the revisability of scientific theories. Then Lakatos's methodology of scientific research programs (SRP) is reinterpreted: The structure of an SRP is a target theory equipped with a priority structure for hypothetical revisions that accommodate idealizing assumptions. Idealizations pointing "backwards" capture predecessor theories, thus showing both their virtues and limitations. The core of an SRP is assigned top priority; its positive heuristics consists in a strategy of how to work off the idealizing assumptions. In the dynamics of SRP's, progressive intertheoretic relations within an SRP are characterized as generating continuity through revisions, while those that hold across SRP's only have excess empirical content. Finally, we contrast our account with a reconstruction of Lakatos's in the structuralist philosophy of science (W. Stegmüller).

Dieser Beitrag vergleicht G. F. Meiers Prinzip der hermeneutischen Billigkeit mit D. Davidsons „Principle of Charity". In der Literatur wurde darauf hingewiesen, daß diese sehr allgemeinen Prinzipien wohlwollender Interpretation insofern verwandt sind, als sie Sprechern und Autoren generell eine gewisse Form von Rationalität unterstellen. Doch weisen sie auch deutlich erkennbare Unterschiede auf. Während Meiers Auslegungskunst einen naiven Bedeutungsbegriff voraussetzt, wirkt Davidsons Prinzip in erster Linie bedeutungskonstitutiv. Ich setze die beiden Prinzipien in den Rahmen einer allgemeinen, hier nur grob entworfenen Theorie der Interpretation, nach der die Interpretation von Äußerungen und Texten stets ein Rekonstruktionsunternehmen darstellt, welches die Existenz von Bedeutungen elementarer lexikalischer Einheiten und grammatikalischer Konstruktionen postuliert, die kontextuell-holistisch verstanden und kompositional verknüpft werden können