Everettian quantum mechanics without branching time

In this paper I assess the prospects for combining contemporary Everettian quantum mechanics (EQM) with branching-time semantics in the tradition of Kripke, Prior, Thomason and Belnap. I begin by outlining the salient features of ??decoherence-based?? EQM, and of the ??consistent histories?? formalism that is particularly apt for conceptual discussions in EQM. This formalism permits of both ??branching worlds?? and ??parallel worlds?? interpretations; the metaphysics of EQM is in this sense underdetermined by the physics. A prominent argument due to Lewis (On the Plurality of Worlds, 1986) supports the non-branching interpretation. Belnap et?al. (Facing the Future: Agents and Choices in Our Indeterministic World, 2001) refer to Lewis?? argument as the ??Assertion problem??, and propose a pragmatic response to it. I argue that their response is unattractively ad hoc and complex, and that it prevents an Everettian who adopts branching-time semantics from making clear sense of objective probability. The upshot is that Everettians are better off without branching-time semantics. I conclude by discussing and rejecting an alternative possible motivation for branching time.     

Temporal necessity and the conditional

In [12] Richmond Thomason and Anil Gupta investigate a semantics for conditional logic that combines the ideas of [8] and [9] with a branching time model of tense logic. The resulting branching time semantics for the conditional is intended to capture the logical relationship between temporal necessity and the conditional. The central principle of this logical relationship is Past Predominance, according to which past similarities and differences take priority over future similarities and differences in determining the comparative similarity of alternative possible histories with respect to a given present moment.In this paper I will use ordinary possible worlds semantics (i.e. Kripke frames) to solve the completeness problem for a system of logic that combines conditional logic with temporal necessity in the context of Past Predominance. Branching time models turn out not to be necessary for the articulation of Past Predominance, and this means that one can axiomatize Past Predominance without first having to solve a much more difficult problem: the completeness problem for the logic of temporal necessity in the context of branching time.Thomason and Gupta argue in [12] that in addition to Past Predominance, temporal necessity and the conditional are logically related, by what have become known as the Edelberg Inferences, whose apparent validity motivates the very complicated theory presented at the end of [12]. I will conclude this paper by examining how the Edelberg inferences would be incorporated into the possible worlds based system presented in the earlier sections of this paper.This article is based on the second chapter of my doctoral dissertation Studies in the Semantics of Modality, University of Pittsburgh, 1985. I thank my adviser Richmond Thomason for his patient help throughout the course of that project.     

Relativism and Two Kinds of Branching Time

This essay examines the case for relativism about future contingents in light of a distinction between two ways of interpreting the ‘branching time’ framework. The first step of the relativist argument is to argue for the ‘Non-Determination Thesis’, the view that there is no unique actual future. The second step is to argue from the Non-Determination Thesis to relativism. I show that first step of this argument fails. But despite that result, the second step is still of interest, because one might hold the Non-Determination Thesis on alternative grounds. I then argue that whether the second step of the argument succeeds depends on how the branches in question are interpreted. If the branches are ersatz possible worlds, then the argument for relativism might go through. But if the branches are concrete parts of a ‘branching multiverse’, then the argument for relativism turns out to make implausible assumptions about the nature of personal identity over time.     

How to evaluate counterfactuals in the quantum world

In the article I discuss possible amendments and corrections to Lewis’s semantics for counterfactuals that are necessary in order to account for the indeterministic and non-local character of the quantum world. I argue that Lewis’s criteria of similarity between possible worlds produce incorrect valuations for alternate-outcome counterfactuals in the EPR case. Later I discuss an alternative semantics which rejects the notion of miraculous events and relies entirely on the comparison of the agreement with respect to individual facts. However, a controversy exists whether to include future indeterministic events in the criteria of similarity. J. Bennett has suggested that an indeterministic event count toward similarity only if it is a result of the same causal chain as in the actual world. I claim that a much better agreement with the demands of the quantum-mechanical indeterminism can be achieved when we stipulate that possible worlds which differ only with respect to indeterministic facts that take place after the antecedent-event should always be treated as equally similar to the actual world. In the article I analyze and dismiss some common-sense counterexamples to this claim. Finally, I critically evaluate Bennett’s proposal regarding the truth-conditions for true-antecedent counterfactuals.     

From Dyad to Triad: On Psychodynamic Meanings of Psychiatric Treatment

The professions of psychiatry and psychotherapy are both complementary and competitive. This paper examines the dialectic tension between the two. It observes the complexity in having psychiatric evaluation and treatment in the context of ongoing psychotherapy. A referral to a psychiatrist is a meaningful, and a charged intrapsychic and interpsychic event for the patient as well as for the two therapists involved. The nature of the triangle is affected by the inner worlds of the three participants; therefore, the more awareness to the shared work, the better the communication between the three sides of this triangle. The referral to a psychiatrist by a psychotherapist is described as a specific type of an enactment in which the therapeutic dyad is becoming a tirade with all the implications attached. As opposed to the dichotomous perception of the psychiatric intervention as a temporary interruption and reduction of the therapy, this paper offers a model of cooperation between professions that will create a wider and deeper therapeutic space.     

A Defense of Egalitarianism

Recently in this journal, Michael Huemer has attempted to refute egalitarianism. His strategy consists in: first, distinguishing between three possible worlds (one with an equal distribution of well-being, one with an unequal distribution at every moment but with an equal distribution overall, and one with an unequal distribution at every moment as well as overall); second, showing that the first world is equal in value to the second world; third, dividing the second and third worlds into two temporal segments each, then showing that none of the temporal segments possesses greater moral value than any other, thereby demonstrating that the second and third worlds as a whole are equal in value; and finally, concluding that none of the three worlds has more value than any other. The present article rebuts Huemer’s critique of egalitarianism first, and most importantly, by showing that his core argument rests upon an equivocation, and second, by refuting his supplementary arguments.     

Pleonastic possible worlds

The role of possible worlds in philosophy is hard to overestimate. Nevertheless, their nature and existence is very controversial. This is particularly serious, since their standard applications depend on there being sufficiently many of them. The paper develops an account of possible worlds on which it is particularly easy to believe in their existence: an account of possible worlds as pleonastic entities. Pleonastic entities are entities whose existence can be validly inferred from statements that neither refer to nor quantify over them as a matter of conceptual necessity. Definitions are proposed that ensure that this is the case for possible worlds.     

Action and Knowledge in Alternating-Time Temporal Logic

Alternating-time temporal logic (ATL) is a branching time temporal logic in which statements about what coalitions of agents can achieve by strategic cooperation can be expressed. Alternating-time temporal epistemic logic (ATEL) extends ATL by adding knowledge modalities, with the usual possible worlds interpretation. This paper investigates how properties of agents’ actions can be expressed in ATL in general, and how properties of the interaction between action and knowledge can be expressed in ATEL in particular. One commonly discussed property is that an agent should know about all available actions, i.e., that the same actions should be available in indiscernible states. Van der Hoek and Wooldridge suggest a syntactic expression of this semantic property. This paper shows that this correspondence in fact does not hold. Furthermore, it is shown that the semantic property is not expressible in ATEL at all. In order to be able to express common and interesting properties of action in general and of the interaction between action and knowledge in particular, a generalization of the coalition modalities of ATL is proposed. The resulting logics, ATL-A and ATEL-A, have increased expressiveness without loosing ATL’s and ATEL’s tractability of model checking.     

Authentic Springs of Action and Obligation

What is the connection between action that is caused by inauthentic antecedent springs of action, such as surreptitiously engineered-in desires and beliefs, and moral obligation? If, for example, an agent performs an action that derives from such antecedent springs can it be that the agent is not obligated to perform this action owing to the inauthenticity of its causal antecedents? I defend an affirmative response, assuming that we morally ought to bring about the states of affairs that occur in the intrinsically best worlds accessible to us and that a version of attitudinal hedonism is the axiology for ranking worlds.     

A General Family of Preferential Belief Removal Operators

Most belief change operators in the AGM tradition assume an underlying plausibility ordering over the possible worlds which is transitive and complete. A unifying structure for these operators, based on supplementing the plausibility ordering with a second, guiding, relation over the worlds was presented in Booth et al. (Artif Intell 174:1339–1368, 2010). However it is not always reasonable to assume completeness of the underlying ordering. In this paper we generalise the structure of Booth et al. (Artif Intell 174:1339–1368, 2010) to allow incomparabilities between worlds. We axiomatise the resulting class of belief removal functions, and show that it includes an important family of removal functions based on finite prioritised belief bases.     

Systems of modal logic for impossible worlds

The intuitive notion behind the usual semantics of most systems of modal logic is that of ‘possible worlds’. Loosely speaking, an expression is necessary if and only if it holds in all possible worlds; it is possible if and only if it holds in some possible world. Of course, contradictory expressions turn out to hold in no possible worlds, and logically true expressions turn out to hold in every possible world. A method is presented for transforming standard modal systems into systems of modal logic for impossible worlds. To each possible world there corresponds an impossible world such that an expression holds in the impossible world if and only if it does not hold in the possible world. One can then talk about such worlds quite consistently, and there seems to be no logical reason for excluding them from consideration.     

What does Batman think about SpongeBob? children's understanding of the fantasy/fantasy distinction

Young children reliably distinguish reality from fantasy; they know that their friends are real and that Batman is not. But it is an open question whether they appreciate, as adults do, that there are multiple fantasy worlds. We test this by asking children and adults about fictional characters' beliefs about other characters who exist either within the same world (e.g., Batman and Robin) or in different worlds (e.g., Batman and SpongeBob). Study 1 found that although both adults and young children distinguish between within-world and across-world types of character relationships, the children make an unexpected mistake: they often claim that Batman thinks that Robin is make believe. Study 2 used a less explicit task, exploring intuitions about the actions of characters-whom they could see, touch, and talk to--and found that children show a mature appreciation of the ontology of fictional worlds.     

Generating possibilities

Our knowledge of the most basic alternative possibilities can be thought of as generated recursively from what we know about the actual world. But what are the generating principles? According to one view, they are recombinational: roughly, alternative possibilities are generated by “patching together” parts of distinct worlds or “blotting out” parts of worlds to yield new worlds. I argue that this view is inadequate. It is difficult to state in a way that is true and non-trivial, and anyway fails to account for our knowledge that there might have been other things, properties, relations, and combinations of these than there actually are. I sketch and defend an alternative view based on the distinction between determinable and determinate properties: roughly, alternative possibilities are generated by “intra-determinable” variation, variation from one determinate to another of the same determinable.     

Reasoning About Collectively Accepted Group Beliefs

A proof-theoretical treatment of collectively accepted group beliefs is presented through a multi-agent sequent system for an axiomatization of the logic of acceptance. The system is based on a labelled sequent calculus for propositional multi-agent epistemic logic with labels that correspond to possible worlds and a notation for internalized accessibility relations between worlds. The system is contraction- and cut-free. Extensions of the basic system are considered, in particular with rules that allow the possibility of operative members or legislators. Completeness with respect to the underlying Kripke semantics follows from a general direct and uniform argument for labelled sequent calculi extended with mathematical rules for frame properties. As an example of the use of the calculus we present an analysis of the discursive dilemma.     

两个世界与历史理念--一种历史观念的考察

两个世界与理性自由的理念构成了古希腊时代以来西方哲学-文化的基本传统和基本精神。这一传统直到马克思哲学产生后才受到了实践批判的深刻挑战。本文对这一历史过程作了概括性考察,认为在两个世界的张力结构与理性自由的基本理念之间存在着深刻的内在关联。本文不同意把持续了数千年之久的这样一种精神传统仅仅批判为唯心主义的简单化做法,认为有必要深入考察这种传统在西方哲学-文化史上的基本意义。在本文看来,两个世界与理性自由的理念在历史的前进发展中不断发生着内容的更新与转换,但只有在马克思唯物史观的实践批判中才得到了彻底的革命性变革。     

Relevant possibilities

There are a number of relevant alternatives accounts of knowledge in the literature, including those by contextualists (like Lewis and Cohen), and invariantists (like Dretske). Despite widespread discussion of such views, an explication of the notion of relevance is conspicuously absent from the literature. Without a careful explication of that notion, relevant alternatives accounts resist evaluation. This paper attempts to aid in the evaluation of those accounts, by providing an account of relevance. The account rejects two common presuppositions about the notion of relevance. The account holds that worlds, rather than alternatives, are relevant, and that distant worlds can be relevant. Relevant worlds turn out to be those worlds at which an alternative to one’s belief obtains, and is such that one’s epistemic position (with respect to what one believes at the actual world) is worse than it is at the actual world.     

The best of all possibleworlds

The Argument from Inferiority holds that our world cannot be the creation of an omnipotent and omnibenevolent being; for if it were, it would be the best of all possible worlds, which evidently it is not. We argue that this argument rests on an implausible principle concerning which worlds it is permissible for an omnipotent being to create: roughly, the principle that such a being ought not to create a non-best world. More specifically, we argue that this principle is plausible only if we assume that there is a best element in the set of all possible worlds. However, as we show, there are conceivable scenarios in which that assumption does not hold.     

Agnosticism About Other Worlds: A New Antirealist Programme in Modality

The modal antirealist, as presented here, aims to secure at least some of the benefits associated with talking in genuine modal realist terms while avoiding commitment to a plurality of Lewisian (or ersatz) worlds. The antirealist stance of agnosticism about other worlds combines acceptance of Lewis's account of what world-talk means with refusal to assert, or believe in, the existence of other worlds. Agnosticism about other worlds does not entail a comprehensive agnosticism about modality, but where such agnosticism about modality is enforced, the aim of the agnostic programme is to show that it is not detrimental to our modal practices. The agnostic programme consists in an attempt to demonstrate the rational dispensability of that disputed class of modal beliefs which the agnostic eschews, but which are held by the realist and the folk. Here I attempt to motivate, describe, and illustrate such an agnostic antirealist programme in modal philosophy.     

'Most Dear to All the Muses': Mapping Tagorean Networks of Enterprise--A Study in Creative Complexity

ABSTRACT: The network of enterprise concept was applied to an "uncontroversially creative" subject from a non-Western culture-Rabindranath Tagore, the 1913 Nobel laureate in literature. The approach followed here is developmental, describing and analyzing the evolution of aspects of the creative work. It reflects historical reconstruction, examining not only the creative products but other phenomenological materials as well; but care is taken to remain sensitive to the multiple contexts in which the individual operated, including work tasks and enterprises; family and private worlds; professional milieus; and the sociohistorical period. The study explains the challenges in mapping Tagore's network of enterprises and analyzes his overall purpose in undertaking creative work. The analysis of Tagore's literary enterprises provided the basis for defining his uniqueness, along with the density, longevity, cyclicity, and branching nature of his enterprises. Furthermore, the realm of drawing and painting provided confirmation of some of the findings obtained from the study of the network of his literary enterprises. -     

Constructing worlds

You and I can differ in what we say, or believe, even though the things we say, or believe, are logically equivalent. Discussing what is said, or believed, requires notions of content which are finer-grained than sets of (metaphysically or logically) possible worlds. In this paper, I develop the approach to fine-grained content in terms of a space of possible and impossible worlds. I give a method for constructing ersatz worlds based on a theory of substantial facts. I show how this theory overcomes an objection to actualist constructions of ersatz worlds and argue that it naturally gives rise to useful notions of fine-grained content.