En una conocida carta redactada en 1671, Leibniz formula un esquema argumental que intenta resolver el problema de la existencia del mal, pero que sorprende por una conclusión necesitarista, según la cual toda la cadena de eventos existentes es la óptima, y por tanto es necesaria. El presente trabajo propone una reconstrucción detallada del argumento y un análisis de su significación modal. Este análisis revela que la necesidad atribuida por Leibniz al mundo actual expresa la fuerza modal que adquiere lo (...) óptimo en su filosofía, ya en 1671, como principio que rige indefectiblemente la acción de Dios. (shrink)

Conceivability arguments constitute a serious threat against reductive physicalism. Recently, a number of authors have proven and characterized a devastating logical truth, centered on these arguments: namely, that their soundness entails the inconceivability of reductive physicalism. In this paper, I demonstrate that is only a logical truth when reductive physicalism is interpreted in its stronger, intrinsic sense, as opposed to its weaker—yet considerably more popular—extrinsic sense. The basic idea generalizes: perhaps surprisingly, stronger forms of reduction are uniquely resistant to the (...) conceivability arguments opposing them. So far as the modal epistemology of reduction is concerned, therefore, it pays to go intrinsic. (shrink)

Robert Alexy's claim that law of necessity has a dual nature raises many interesting philosophical questions. In this article, I consider some of these questions, such as what the meaning of the correctness thesis is, whether Alexy's discourse theory supports this thesis, and whether the thesis is defensible; whether Alexy's argument from anarchy and civil war supports the claim that law of necessity has a real dimension; and what the implications are of the use of moral arguments, such as the (...) argument from injustice, for the status of Alexy's inquiry. (shrink)

In this paper, I will develop a new theory of the nature of happiness, or “perfect happiness.” I will examine what perfect happiness is and what it is not and I will try to answer some fundamental questions about this property. According to the theory, which I shall call “the fulfillment theory,” perfect happiness is perfect fulfillment. The analysis of happiness in this paper is a development of the old idea that happiness is getting what you want and can be (...) classified as a kind of desire-satisfaction theory. According to the fulfillment theory of happiness, it is necessarily the case that an individual x is perfectly happy if and only if all x’s wants are fulfilled. The interpretation of this basic definition is important, since the consequences of the particular version defended in this essay are radically different from the consequences of many other popular theories of happiness. The fulfillment theory is also quite different from most other desire-satisfaction theories of happiness. We will see that it has many interesting consequences and that it can be defended against some potentially serious counterarguments. The upshot is that the analysis of (perfect) happiness developed in the present paper is quite attractive. (shrink)

In this paper, I develop a new set of doxastic logical systems and I show how they can be used to solve several well-known problems in doxastic logic, for example the so-called problem of logical omniscience. According to this puzzle, the notions of knowledge and belief that are used in ordinary epistemic and doxastic symbolic systems are too idealised. Hence, those systems cannot be used to model ordinary human or human-like agents' beliefs. At best, they can describe idealised individuals. The (...) systems in this paper can be used to symbolise not only the doxastic states of perfectly rational individuals, but also the beliefs of finite humans. Proof-theoretically, I will use a tableau technique. Every system is combined with predicate logic with necessary identity and ‘possibilist’ quantifiers and modal logic with two kinds of modal operators for relative and absolute necessity. The semantics is a possible world semantics. Finally, I prove that every tableau system in the paper is sound and complete with respect to its semantics. (shrink)

Against the background of the theory of branching space-times (BST), the paper sketches a concept of individuals. It discusses Kripkean modal intuitions concerning individuation, and, finally it addresses Lewis’s objections to branching individuals.

I argue that metaphysicians of mind have not done justice to the notion of accessibility between possible worlds. Once accessibility is given its due, physicalism must be reformulated and conceivability arguments must be reevaluated. To reach these conclusions, I explore a novel way of assessing the zombie conceivability argument. I accept that zombies are possible and ask whether that possibility is accessible from our world in the sense of ‘accessible’ used in possible world semantics. It turns out that the question (...) whether zombie worlds are accessible from our world is equivalent to the question whether physicalism is true at our world. By assuming that zombie worlds are accessible from our world, proponents of the zombie conceivability argument beg the question against physicalism. In other words, it is a mistake to assume that the metaphysical possibility of zombies entails that physicalism is false at our world. I will then consider what happens if a proponent of the zombie conceivability argument should insist that zombie worlds are accessible from our world. I will argue that the same ingredients used in the zombie conceivability argument—whatever exactly they might be—can be used to construct an argument to the opposite conclusion. At that point, we reach a stalemate between physicalism and property dualism: while the possibility of zombies entails property dualism, the possibility of other creatures entails physicalism. Since these two possibilities are mutually inconsistent, either one of them is not genuine or one of them is inaccessible from the actual world. To resolve this stalemate, we need more than traditional conceivability arguments. (shrink)

This research article revisits Hempel’s logic of confirmation in light of recent developments in categorical proof theory. While Hempel advocated several logical conditions in favor of a purely syntactical definition of a general non-quantitative concept of confirmation, we show how these criteria can be associated to specific logical properties of monoidal modal deductive systems. In addition, we show that many problems in confirmation logic, such as the tacked disjunction, the problem of weakening with background knowledge and the problem of irrelevant (...) conjunction, are also associated with specific logical properties and, incidentally, with some of Hempel’s logical conditions of adequacy. We discuss the raven paradox together with further objections against Hempel’s approach, showing how our analysis enables a clear understanding of the relationships between Hempel’s conditions, the problems in confirmation logic, and the properties of deductive systems. (shrink)

This essay introduces a puzzle about the interaction between quantifiers and epistemic modals. The puzzle motivates the idea that whether an object satisfies an epistemically modalized predicate depends on the mode of presentation of the domain of quantification. I compare two ways of implementing this idea, one using counterpart theory, the other using Aloni's 'conceptual covers' theory, and then provides some evidence in favor of the former.

I argue that propositions are contingent existents. Some propositions that in fact exist might not have existed and there might have been propositions that are distinct from every actually existing proposition. This is because some propositions are singular propositions, which are propositions containing ordinary objects as constituents, and so are ontologically dependent on the existence of those objects; had those objects not existed, then the singular propositions would not have existed. I provide both a philosophical and technical understanding of the (...) contingent status of propositions. (shrink)

According to strong pluralism, objects distinct by virtue of their modal properties can coincide. The most common objection towards such view invokes the so-called Grounding Problem according to which the strong pluralist needs to explain what the grounds are for supposed modal differences between the coincidents. As recognized in the literature, the failure to provide an answer to the Grounding Problem critically undermines the plausibility of strong pluralism. Moreover, there are strong reasons to believe that strong pluralists cannot provide an (...) explanation of the Grounding Problem. In this paper, we argue that strong pluralism can be motivated independently of the successful answer to the Grounding Problem. In order to achieve that aim, we provide a haecceitistic interpretation of strong pluralism according to which strong pluralism should be read as a position committed to the existence of primitive individuals, i.e., the individuals that have their criteria of individuation independently of their qualitative profiles. That said, we do not aim at defending haecceitism. Instead, our aim is rather modest: we want to provide a new way for the strong pluralist to supplement his view to make it more watertight. (shrink)

This paper presents rules in sequent calculus for a binary quantifier I to formalise definite descriptions: Ix[F, G] means ‘The F is G’. The rules are suitable to be added to a system of positive free logic. The paper extends the proof of a cut elimination theorem for this system by Indrzejczak by proving the cases for the rules of I. There are also brief comparisons of the present approach to the more common one that formalises definite descriptions with a (...) term forming operator. In the final section rules for I for negative free and classical logic are also mentioned. (shrink)

Gentzen’s and Jaśkowski’s formulations of natural deduction are logically equivalent in the normal sense of those words. However, Gentzen’s formulation more straightforwardly lends itself both to a normalization theorem and to a theory of “meaning” for connectives . The present paper investigates cases where Jaskowski’s formulation seems better suited. These cases range from the phenomenology and epistemology of proof construction to the ways to incorporate novel logical connectives into the language. We close with a demonstration of this latter aspect by (...) considering a Sheffer function for intuitionistic logic. (shrink)

We present a proof of the equivalence between two deductive systems for constructive necessity, namely an axiomatic characterisation inspired by Hakli and Negri's system of derivations from assumptions for modal logic , a Hilbert-style formalism designed to ensure the validity of the deduction theorem, and the judgmental reconstruction given by Pfenning and Davies by means of a natural deduction approach that makes a distinction between valid and true formulae, constructively. Both systems and the proof of their equivalence are formally verified (...) using the state-of-the-art proof assistant Coq. The proof approach taken throughout the paper unveils the use of some alternative proof methods that allow for a smooth transition from the high-level mathematical proofs to their mechanised counterparts. (shrink)

Perner and Roessler Causing human action: new perspectives on the causal theory of action, MIT Press, Cambridge, MA, pp 199–228, 2010) hold that children who do not yet have an understanding of subjective perspectives, i.e., mental states, explain actions by appealing to objective facts. In this paper, we criticize this view. We argue that in order to understand objective facts, subjects need to understand perspectives. By analysing basic fact-expressing assertions, we show that subjects cannot refer to facts if they do (...) not understand two types of perspectivity, namely, spatial and doxastic perspectivity. To avoid conceptual confusion regarding different ways of referring to facts, we distinguish between reference to facts de re and de dicto. (shrink)

This paper will present two contributions to teaching introductory logic. The first contribution is an alternative tree proof method that differs from the traditional one-sided tree method. The second contribution combines this tree system with an index system to produce a user-friendly tree method for sentential modal logic.

An intuitive objection to modal realism is that merely possible worlds and their inhabitants seem to be irrelevant to an analysis of modality. Kripke originally phrased the objection in terms of being concerned about one’s modal properties without being concerned about the properties one’s other-worldly counterparts have. The author assesses this objection in a variety of forms, and then provides his own formulation that does not beg the question against the modal realist. Finally, the author considers two potential answers to (...) the objection so understood and concludes that only one of them has a chance of succeeding. (shrink)

I show that intuitive and logical considerations do not justify introducing Leibniz’s Law of the Indiscernibility of Identicals in more than a limited form, as applying to atomic formulas. Once this is accepted, it follows that Leibniz’s Law generalises to all formulas of the first-order Predicate Calculus but not to modal formulas. Among other things, identity turns out to be logically contingent.

Habilitation thesis in psychology. The book consists of a collection of reasoning studies. The experimental investigations will take us from people’s reasoning about probabilities, entailments, pragmatic factors, argumentation, and causality to morality. An overarching theme of the book is norm pluralism and individual differences in rationality research.

This chapter presents a new semantics for inductive empirical knowledge. The epistemic agent is represented concretely as a learner who processes new inputs through time and who forms new beliefs from those inputs by means of a concrete, computable learning program. The agent’s belief state is represented hyper-intensionally as a set of time-indexed sentences. Knowledge is interpreted as avoidance of error in the limit and as having converged to true belief from the present time onward. Familiar topics are re-examined within (...) the semantics, such as inductive skepticism, the logic of discovery, Duhem’s problem, the articulation of theories by auxiliary hypotheses, the role of serendipity in scientific knowledge, Fitch’s paradox, deductive closure of knowability, whether one can know inductively that one knows inductively, whether one can know inductively that one does not know inductively, and whether expert instruction can spread common inductive knowledge—as opposed to mere, true belief—through a community of gullible pupils. (shrink)

The notion of validity for modal languages could be defined in two slightly different ways. The first is the original definition given by S. Kripke, for which a formula φ of a modal language L is valid if and only if it is true in every actual world of every interpretation of L. The second is the definition that has become standard in most textbook presentations of modal logic, for which a formula φ of L is valid if and only (...) if it is true in every world in every interpretation of L. For simple modal languages, “Kripkean validity” and “Textbook validity” are extensionally equivalent. According to E. Zalta, however, Textbook validity is an “incorrect” definition of validity, because: (i) it is not in full compliance with Tarski’s notion of truth; (ii) in expressively richer languages, enriched by the actuality operator, some obviously true formulas count as valid only if the Kripkean notion is used. The purpose of this paper is to show that (i) and (ii) are not good reasons to favor Kripkean valid- ity over Textbook validity. On the one hand, I will claim that the difference between the two should rather be seen as the result of two different conceptions on how a modal logic should be built from a non-modal basis; on the other, I will show the advantages, for the question at issue, of seeing the actuality operator as belonging to the family of two-dimensional operators. (shrink)

We give a brief introduction to the axiomatization of temporal logics. Branching continuations are shortly presented thereafter and the possibility of their clear syntactical axiomatization in a Hilbert-style system is investigated as last. Some basic preliminary observations and suggestions, how such axiomatization could start, are presented.