Thomas Müller

The metaphor of a branching tree of future possibilities has a number of important philosophical and logical uses. In this paper we trace this metaphor through some of its uses and argue that the metaphor works the same way in physics as in philosophy. We then give an overview of formal systems for branching possibilities, viz., branching time and (briefly) branching space-times. In a next step we describe a number of different notions of possibility, thereby sketching a landscape of possibilities. In the final section of the paper we look at the place of branching-based possibilities in that larger landscape of possibilities. Our main message is that far from being an outlandish metaphysical extravagancy, branching-based possibilities are epistemically as well as metaphysically basic.

The paper gives a physicist's view on the framework of branching space-time, 385--434). Branching models are constructed from physical state assignments. The models are then employed to give a formal semantics for the modal operators ``possibly'' and ``necessarily'' and for the counterfactual conditional. The resulting formal language can be used to analyze quantum correlation experiments. As an application sketch, Stapp's premises LOC1 and LOC2 from his purported proof of non-locality, 300--304) are analyzed

Prior's project of tense logic has both a formal-logical and a philosophical side. Both aspects were important for Prior. The paper suggests viewing Prior's philosophical project as a continuation of the tradition of "logic as language", or "universalism", identified by van Heijenoort and Hintikka, respectively. The label "tense-logical universalism" is chosen in order to stress Prior's emphasis on the foundational role of natural language for the three fields of logic, semantics, and philosophy of science. The paper draws on Prior's works in all three mentioned areas. In particular, we comment on Prior's universalist approach to model theory, which has recently given rise to hybrid logic, and on the interesting perspective on relativity theory offered through his writings.

Towards the end of her famous 1971 paper “Causality and Determination”, Elizabeth Anscombe discusses the controversial idea that “ ‘physical haphazard’ could be the only physical correlate of human freedom of action”. In order to illustrate how the high-level freedom of human action can go together with micro-indeterminism without creating a problem for micro-statistics, she provides the analogy of a glass box filled with minute coloured particles whose micro-dynamics is subject to statistical laws, while its outside reliably displays a recognisable variation of a certain image created by an external cause. Anscombe’s example is somewhat enigmatic, and she provides no details to support its viability. In this paper we discuss the context of Anscombe’s analogy, and we provide basics of the theory and practice of building an Anscombe box.

In this paper we describe a novel approach to defining an ontologically fundamental notion of co-presentness that does not go against the tenets of relativity theory. We survey the possible reactions to the problem of the present in relativity theory, introducing a terminological distinction between a static role of the present, which is served by the relation of simultaneity, and a dynamic role of the present, with the corresponding relation of co-presentness. We argue that both of these relations need to be equivalence relations, but they need not coincide. Simultaneity, the sharing of a temporal coordinate, need not have fundamental ontological import, so that a relativizing strategy with respect to simultaneity seems promising. The notion of co-presentness, on the other hand, does have ontological import, and can therefore not be relativized to an observer or to an arbitrarily chosen frame. We argue that a formal representation of indeterminism can provide the structure needed to anchor the relation of co-presentness, and that this addition is in fact congenial to the notion of dynamic time as requiring real change. The resulting picture is one of an extended dynamic present, implying a formal distinction between static simultaneity and dynamic co-presentness. After working out the basics of our approach in the simpler framework of branching time, we provide our full analysis in the framework of branching space-times, which allows for a formal definition of modal correlations. The spatial extension of the dynamic present can reach as far as the modal correlations do. In the limit, the dynamic present could extend across a maximal space-like hypersurface.

Anscombe’s 1971 inaugural lecture at Cambridge, entitled ‘Causality and Determination’, has had a lasting influence on a remarkably broad range of philosophers and philosophical debates, touching on fundamental topics in philosophy of science, action theory, the free will debate, epistemology, philosophy of mind, and metaphysics. Especially where anti-reductionist or pluralist strands of philosophical thought are being seriously considered, one should not be surprised to find references to Anscombe’s lecture. Moreover, there appears to be a growing interest in Anscombe’s comprehensive philosophical outlook, as attested by the recent publication of a weighty collection of essays spanning that outlook in its full breadth in the prestigious Routledge Philosophical Minds series. Against this background it is apt that now, 50 years after the original lecture, a Topical Collection sees the light, circling around the most central themes from Anscombe’s lecture, with a particular emphasis on the question how these hang together, how they form part of the larger philosophical project that Anscombe obviously intended the lecture to highlight. This Introduction motivates the Topical Collection, and introduces the various contributions against that background.

Branching space-times (BST; Belnap, Synthese 92:385–434, 1992 ) is the most advanced formal framework for representing indeterminism. BST is however based on continuous partial orderings, while our natural way of describing indeterministic scenarios may be called discrete. This paper establishes a theorem providing a discrete data format for BST: it is proved that a discrete representation of indeterministic scenarios leading to BST models is possible in an important subclass of cases. This result enables the representation of limited indeterminism in BST and hopefully paves the way for the representation of substances with capacities in that framework

The present volume contains primarily the invited papers of the 28th Inter-national Wittgenstein Symposium that was held in Kirchberg am Wech-sel (Lower Austria) in August 2005. It was dedicated to the topic Time and History (Zeit und Geschichte) in an interdisciplinary perspective, ranging from the philosophy of time, in the narrower sense, the approaches of the single scientific disciplines, in so far as they are informed by foundational and philosophical issues, to culture and art. As usual, the contributed papers (Beitr age) were already published prior to the symposium. While the latter volume contains, in a special section, papers dedicated to all aspects of Wittgenstein's work, the present volume focuses on his views about time. The editors are well aware that both time and history are prominently discussed within the phenomenological and hermeneutic traditions in philosophy. This was well reflected in the contributed papers, as can be seen in the Beitr age volume, and in some papers dealing with time and history from a cultural perspective. For reasons of thematic coherence and as a consequence of the general orientation of this book series, however, the editors have given priority to philosophers belonging to the analytic tradition in the broad sense. The editors nonetheless hope to have succeeded in presenting an equally focused and comprehensive picture of the contemporary debate.

Since the validity of Bell's inequalities implies the existence of joint probabilities for non-commuting observables, there is no universal consensus as to what the violation of these inequalities signifies. While the majority view is that the violation teaches us an important lesson about the possibility of explanations, if not about metaphysical issues, there is also a minimalist position claiming that the violation is to be expected from simple facts about probability theory. This minimalist position is backed by theorems due to A. Fine and I. Pitowsky.Our paper shows that the minimalist position cannot be sustained. To this end,we give a formally rigorous interpretation of joint probabilities in thecombined modal and spatiotemporal framework of `stochastic outcomes inbranching space-time' (SOBST) (Kowalski and Placek, 1999; Placek, 2000). We show in this framework that the claim that there can be no joint probabilities fornon-commuting observables is incorrect. The lesson from Fine's theorem is notthat Bell's inequalities will be violated anyhow, but that an adequate modelfor the Bell/Aspect experiment must not define global joint probabilities. Thus we investigate the class of stochastic hidden variable models, whichprima facie do not define such joint probabilities. The reasonwhy these models fail supports the majority view: Bell's inequalities are notjust a mathematical artifact.

The theory of branching space-times is designed as a rigorous framework for modelling indeterminism in a relativistically sound way. In that framework there is room for "funny business", i.e., modal correlations such as occur through quantummechanical entanglement. This paper extends previous work by Belnap on notions of "funny business". We provide two generalized definitions of "funny business". Combinatorial funny business can be characterized as "absence of prima facie consistent scenarios", while explanatory funny business characterizes situations in which no localized explanation of inconsistency can be given. These two definitions of funny business are proved to be equivalent, and we provide an example that shows them to be strictly more general than the previously available definitions of "funny business"

Branching theories are popular frameworks for modeling objective indeterminism in the form of a future of open possibilities. In such theories, the notion of a history plays a crucial role: it is both a basic ingredient in the axiomatic definition of the framework, and it is used as a parameter of truth in semantics for languages with a future tense. Furthermore, histories—complete possible courses of events—ground the notion of modal consistency: a set of events is modally consistent iff there is a history containing that set. We will explain these roles of histories and highlight some critical aspects having to do with the fact that histories are global and, in a relevant sense, “big” objects. The notion of modal consistency, on the other hand, has both local and global aspects. We ask in how far a local notion of modal consistency can serve as an alternative to the common uses of histories, and work out two recent approaches to alternatives to histories. Combining these approaches, we develop a novel semantics for branching time

The logical theory of branching space-times, which is intended to provide a framework for studying objective indeterminism, remains at a certain distance from the discussion of space-time theories in the philosophy of physics. In a welcome attempt to clarify the connection, Earman has recently found fault with the branching approach and suggested ``pruning some branches from branching space-time''. The present note identifies the different---order theoretic vs. topological---points of view of both discussion as a reason for certain misunderstandings, and tries to remove them. Most importantly, we give a novel, topological criterion of modal consistency that usefully generalizes the order-theoretic criterion of directedness, and we introduce a differential-geometrical version of BST based on the theory of non-Hausdorff manifolds.

Pereboom’s ‘wild coincidences’ argument against agent-causal libertarianism is based on the claim that in a world governed by statistical laws, the dovetailing of indeterministic physical happenings with the free actions of agent causes would be a coincidence too wild to be credible. In this paper it is shown that the conclusion is valid for deterministic laws, but that it fails for statistical laws. Therefore, the ‘wild coincidences’ argument does not provide the promised empirical refutation of agent-causal libertarianism.

We provide a formally rigorous framework for integrating singular causation, as understood by Nuel Belnap's theory of causae causantes, and objective single case probabilities. The central notion is that of a causal probability space whose sample space consists of causal alternatives. Such a probability space is generally not isomorphic to a product space. We give a causally motivated statement of the Markov condition and an analysis of the concept of screening-off. 1. Causal dependencies and probabilities1.1Background: causation in branching space-times1.2What are probabilities defined for?2. Basic transitions2.1Basics of basic transitions2.2Sets of basic transitions3. Causal probability theory3.1Some simple cases3.2General causal probabilities3.3Application: probability of suprema of a chain.

This paper aims at bringing together two debates in metaphysics that so far have been kept separate: the debate about determinism vs. indeterminism as de re modality on the one hand, and the debate about persistence on the other hand. Both debates significantly involve talk of things. We will show that working out a proper semantics for singular terms and an accompanying theory of things, motivated by considerations of quantified modal logic, can significantly further the persistence debate. We will use our semantic framework to give an argument in support of the endurantist position as the best theory of persistence

Theories of free agency based on indeterminism -- that is, libertarian theories -- are often accused of undermining an agent's integrity: If an action is due to indeterministic happenings, how can it be called the agent's action to begin with? Isn't a deterministic connection between an agent's circumstances and her action needed to maintain her integrity? We claim that a meaningful notion of agency does not need determinism. In this paper we introduce stochastic libertarianism, a novel theory of free agency under indeterminism. Based on a physically motivated, stochastic model of the temporal evolution of a deliberation process, stochastic libertarianism views indeterminism as a core resource for meaningful agency rather than as a threat. We counter the supposed threat by explicitly discussing Van Inwagen's replay argument, exposing a flaw in the argument that is due to insufficient attention to temporal details. Our approach can also explain how a stochastically libertarian agent developing over time can exhibit highly realiable behavior. We claim, therefore, that integrity in action does not need determinism.

Can we sensibly attribute some of the happenings in our world to the agency of some of the things around us? We do this all the time, but there are conceptual challenges purporting to show that attributable agency, and specifically one of its most important subspecies, human free agency, is incoherent. We address these challenges in a novel way: rather than merely rebutting specific arguments, we discuss a concrete model that we claim positively illustrates attributable agency in an indeterministic setting. The model, recently introduced by one of the authors in the context of artificial intelligence, shows that an agent with a sufficiently complex memory organization can employ indeterministic happenings in a meaningful way. We claim that these considerations successfully counter arguments against the coherence of libertarian free will.

This is part I of a two-part essay introducing case-intensional first order logic, an easy-to-use, uniform, powerful, and useful combination of first-order logic with modal logic resulting from philosophical and technical modifications of Bressan’s General interpreted modal calculus. CIFOL starts with a set of cases; each expression has an extension in each case and an intension, which is the function from the cases to the respective case-relative extensions. Predication is intensional; identity is extensional. Definite descriptions are context-independent terms, and lambda-predicates and -operators can be introduced without constraints. These logical resources allow one to define, within CIFOL, important properties of properties, viz., extensionality and absoluteness, Bressan’s chief innovation that allows tracing an individual across cases without recourse to any notion of “rigid designation” or “trans-world identity.” Thereby CIFOL abstains from incorporating any metaphysical principles into the quantificational machinery, unlike extant frameworks of quantified modal logic. We claim that this neutrality makes CIFOL a useful tool for discussing both metaphysical and scientific arguments involving modality and quantification, and we illustrate by discussing in diagrammatic detail a number of such arguments involving the extensional identification of individuals via absolute properties, essential properties, de re vs. de dicto, and the results of possible tests.

The aim of this paper is to establish that free agency, which is a capacity of many animals including human beings, is compatible with indeterminism: an indeterministic world allows for the existence of free agency. The question of the compatibility of free agency and indeterminism is less discussed than its mirror image, the question of the compatibility of free agency and determinism. It is, however, of great importance for our self-conception as free agents in our (arguably) indeterministic world. We begin by explicating the notions of indeterminism and free agency and by clarifying the interrelation of free agency and the human-specific notion of free will. We then situate our claim of the compatibility of free agency and indeterminism precisely in the landscape of the current debate on freedom and determinism, exposing an unhappy asymmetry in that debate. Then we proceed to make our case by describing the mathematically precise, physically motivated model of projective simulation, which employs indeterminism as a central resource for agency modeling. We argue that an indeterministic process of deliberation modeled by the dynamics of projective simulation can exemplify free agency under indeterminism, thereby establishing our compatibility claim: Free agency can develop and thrive in an indeterministic world.