Elke Brendel (Bonn) gives a talk at the MCMP Colloquium (17 June, 2015) titled "Disagreement and Epistemic Modality". Abstract: Intuitively, the truth conditions of sentences with epistemic modals, such as “It might be that p”, depend on what is epistemically known by a speaker or some contextually relevant group. That is why a contextualist account of epistemic modals seems to provide an adequate semantics for epistemic modal claims. However, contextualism has difficulties to account for the intuition of disagreement about epistemic modal claims: If A claims (according to his knowledge): “It might be that p” and B claims (according to her knowledge) “It cannot be that p”, A and B seem to disagree. They are not merely talking past each other. In my talk, I will first explore the notion of disagreement and present some necessary conditions for two parties disagreeing with each other. Second, I will critically examine the prospects of contextualist semantics as well as truth-relativist accounts in dealing with disagreement about epistemic modal claims. I will finally analyze arguments in favor of an invariantist theory of epistemic modality.
Jun 29, 2015
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Ben Levinstein (Oxford) gives a talk at the MCMP Colloquium (6 May, 2015) titled "A Pragmatic Vindication of Epistemic Utility Theory". Abstract: Traditionally, probabilism and other norms on partial belief have been motivated from a pragmatic point of view. For instance, as Frank Ramsey long ago showed, if you're probabilistically incoherent, then you're subject to a set of bets each of which you consider fair but which are jointly guaranteed to result in a net loss. Since Joyce's seminal 1998 paper, some epistemologists have shifted course and have tried to establish norms on epistemic states without any recourse to practical rationality. I use a theorem from Schervish to bridge the gap between these two approaches. We can either take standard measures of accuracy to be formalizations of purely epistemic value, or we can generate them from what are at base practical foundations. Even if we opt for this latter approach, I show we can mostly cordon off the epistemic from the practical while ultimately grounding epistemic norms in purely practical rationality.
May 11, 2015
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Denis Bonnay (Paris Quest/IHPST) gives a talk at the MCMP Colloquium (30 April, 2015) titled "An Axiomatization of Individual and Social Updates". Abstract: In this talk, I will consider update rules, which an agent may follow in order to update her subjective probabilities and take into account new information she receives. I will consider two different situations in which this may happen: (1) individual updates: when an agent learns the probability for a particular event to have a certain value. (2) social updates: when an agent learns the probability an other agent's gives to a particular event. Jeffrey's conditioning and weighted averaging are two famous update rules, in individual and social situations respectively. I will show that both can be axiomatized by means of one and the same invariance principle, related to Carnap's use of invariance in his work on probabilities.
May 4, 2015
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Greg Gandenberger (Pittsburgh) gives a talk at the MCMP Colloquium (22 April, 2015) titled "New Responses to Some Purported Counterexamples to Likelihoodist Principles". Abstract: The Likelihood Principle is important because the frequentist statistical methods that are most commonly used in science violate it, while rival likelihoodist and Bayesian methods do not. It is supported by a variety of arguments, including several proofs from intuitively plausible axioms. It also faces many objections, including several purported counterexamples. In this talk, I provide new responses to four purported counterexamples to the Likelihood Principle and its near-corollary the Law of Likelihood that are not adequately addressed in the existing literature. I first respond to examples due to Fitelson and Titelbaum that I argue are adequately addressed by restricting the Law of Likelihood to mutually exclusive hypotheses. I then respond to two counterexamples from the statistical literature. My responses to these latter examples are novel in that they do not appeal to prior probabilities, which is important for attempts to use the Likelihood Principle to provide an argument for Bayesian approaches that does presuppose the permissibility of using prior probabilities in science.
May 4, 2015
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Michael Weisberg (Pennsylvania) gives a talk at the Conference on Agent-Based Modeling in Philosophy (11-13 December, 2014) titled "Agent-based Models and Confirmation Theory". Abstract: Is it possible to develop a confirmation theory for agent-based models? The are good reasons to be skeptical: Classical confirmation theory explains how empirical evidence bears on the truth of hypotheses and theories, while agent-based models are almost always idealized and hence known to be false. Moreover, classical ideas about confirmation have been developed for relatively simple hypotheses, while even the simplest agent-based models have thousands of variables. Nevertheless, we can draw on ideas from confirmation theory in order to develop an account of agent-based model confirmation. Theorists can confirm hypotheses about model/world relations, and they can also use a variety of techniques to investigate the reliability of model results. This paper is an exploration of these possibilities.
Jan 28, 2015
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Kevin Zollman (CMU) gives a talk at the Conference on Agent-Based Modeling in Philosophy (11-13 December, 2014) titled "The Formation of Epistemic Networks". Abstract: One important area of study for social epistemology is the social structure epistemic groups -- who communicates their knowledge with whom? Significant research has been done on better and worse communication networks, but less has been done on how a group comes to have one network or another. In this talk, I will present a number of results (some recent) from economics and philosophy about how individuals choose with whom to communicate. Understanding how individuals decide where to gain information can help us to design institutions that lead to epistemically more reliable groups.
Jan 8, 2015
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Scott Page (Michigan) gives a talk at the Conference on Agent-Based Modeling in Philosophy (11-13 December, 2014) titled "Collective Accuracy: Agent Based & Emergent vs Statistical and Assumed". Abstract: In this talk, I describe two broad classes of models that can explain collective accuracy, what is more commonly referred to as the wisdom of crowds. The first model is based on statistical/law of large numbers logic. Accuracy emerges from the cancellation of random errors. The second model has roots in computer science and psychology. It assumes that predictions come from models. Different predictions arise because of different model. I then describe how in agent based models the amount model diversity, and therefore the accuracy of the collective emerges. It is possible to write difference equations that explain average diversity levels. The talk will summarize papers written with Lu Hong, Maria Riolo, PJ Lamberson, and Evan Economo.
Jan 8, 2015
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Aidan Lyon (Maryland, MCMP) gives a talk at the MCMP Colloquium (13 November, 2014) titled "I Believe I don't Believe. (And So Can You!)". Abstract: Contemporary epistemology offers us two very different accounts of our epistemic lives. According to Traditional epistemologists, the decisions that we make are motivated by our desires and guided by our beliefs and these beliefs and desires all come in an all-or-nothing form. In contrast, many Bayesian epistemologists say that these beliefs and desires come in degrees and that they should be understood as subjective probabilities and utilities. What are we to make of these different epistemologies? Are the Tradionalists and the Bayesians in disagreement, or are their views compatible with each other? Some Bayesians have challenged the Traditionalists: Bayesian epistemology is more powerful and more general than the Traditional theory, and so we should abandon the notion of all-or-nothing belief as something worthy of philosophical analysis. The Traditionalists have responded to this challenge in various ways. I shall argue that these responses are inadequate and that the challenge lives on.
Dec 2, 2014
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Jon Williamson (Kent) gives a talk at the MCMP Colloquium (8 October, 2014) titled "The Principal Principle implies the Principle of Indifference". Abstract: I'll argue that David Lewis' Principal Principle implies a version of the Principle of Indifference. The same is true for similar principles which need to appeal to the concept of admissibility. Such principles are thus in accord with objective Bayesianism, but in tension with subjective Bayesianism. One might try to avoid this conclusion by disavowing the link between conditional beliefs and conditional probabilities that is almost universally endorsed by Bayesians. I'll explain why this move offers no succour to the subjectivist.
Oct 13, 2014
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Branden Fitelson (Rutgers) meets Hannes Leitgeb (MCMP/LMU) in a joint session on "Belief vs Probability" at the MCMP workshop "Bridges 2014" (2 and 3 Sept, 2014, German House, New York City). The 2-day trans-continental meeting in mathematical philosophy focused on inter-theoretical relations thereby connecting form and content of this philosophical exchange. Idea and motivation: We use theories to explain, to predict and to instruct, to talk about our world and order the objects therein. Different theories deliberately emphasize different aspects of an object, purposefully utilize different formal methods, and necessarily confine their attention to a distinct field of interest. The desire to enlarge knowledge by combining two theories presents a research community with the task of building bridges between the structures and theoretical entities on both sides. Especially if no background theory is available as yet, this becomes a question of principle and of philosophical groundwork: If there are any – what are the inter-theoretical relations to look like? Will a unified theory possibly adjudicate between monist and dualist positions? Under what circumstances will partial translations suffice? Can the ontological status of inter-theoretical relations inform us about inter-object relations in the world? Find more about the meeting at www.lmu.de/bridges2014.
Sep 11, 2014
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