# Program

The entire conference takes place in room CZ 109, in the Cobbenhagen Building. For directions on campus, click here.

Conference program pdf.

## Conference Program

09:30 - 10:00 | Registration |
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10:00 - 11:30 | Opening and René Descartes Lecture I |

Hannes Leitgeb (LMU Munich): The Humean Thesis of Belief | |

11:30 - 12:00 | Coffee break |

12:00 - 13:00 | Commentary by Richard Pettigrew (Bristol University) |

13:00 - 14:00 | Lunch break |

14:00 - 16:00 | Contributed Talks (abstracts can be found below) |

Pavel Janda (Bristol University): Reflection Principle and Epistemic Utility of Future Contingents | |

Ted Shear and Branden Fitelson (Rutgers University): Diachronic Norms of Rational Full-Belief and the Pressure Toward Stability | |

Kevin Kelly and Konstantin Genin (Carnegie Mellon University): An epistemic justification of Ockham's razor | |

16:00 - 16:30 | Coffee break |

16:30 - 17:50 | Contributed Talks (abstracts can be found below) |

Lasha Abzianidze (TiLPS) | |

Leszek Wronski (Jagiellonian University Krakow): Constraints on credences in two not mutually exclusive propositions: the search for the best belief update function | |

17:50 - 18:30 | Welcome Reception (Dante Building room DZ 5) |

### Abstracts contributed talks Monday, 20 October

### Pavel Janda: Reflection Principle and Epistemic Utility of ...

### Reflection Principle and Epistemic Utility of Future Contingents

We will argue that epistemic utility theory (EUT) combined with MacFarlane's semantics for future contingents creates a clash between two epistemic principles: Reflection Principle and minimization of inaccuracy. We will show that the credence that minimizes an agent's inaccuracy is not the one recommended by the Reflection Principle.### Ted Shear & Branden Fitelson: Diachronic Norms of Rational ...

Ted Shear and Branden Fitelson

### Diachronic Norms of Rational Full-Belief and the Pressure Toward Stability

In this paper, we investigate an accuracy-based treatment of short-term diachronic epistemic norms on rational full-belief. Our account treats epistemic actions as good in so far as they increase the truthlikeness of the agent’s corpus and are bad in so far as they increase its falselikeness. We maintain that an agent ought to perform an epistemic action just in case it maximizes expected movement towards truth and minimizes expected movement towards falsehood. In this paper, we provide an epistemic decision theory for epistemic actions in a way that results in a pressure towards the stability of full-beliefs. The scoring rule that we rely on is an adaptation of the synchronic scoring rule presented in Easwaran (2014). Our treatment provides an account of how partial-belief constrains virtuous revision of full-belief without accepting that either can be reduced to the other.

### Kevin Kelly & Konstantin Genin: An epistemic justification of ...

Kevin Kelly and Konstantin Genin

### An epistemic justification of Ockham's razor

Ockham's razor sanctions a preference for the simpler theory compatible with the data. But can that familiar inductive principle be justified? Justifying an epistemic principle requires answering an epistemic question: why are parsimonious theories more likely to be true? (Baker, 2013). However, no inductive inference principle can guarantee a non-trivial upper bound on chance of error over all possibilities compatible with current information. Reliability, or truth-conductiveness, must be understood dynamically: as maximally direct pursuit of truth, even when there is no guarantee that the current conjecture is true. It is not reliable, in that sense, to reverse course more than necessary, to travel in needless circles, or to abandon the truth after one has found it. A method violating the latter desideratum is called unstable. Stability traces its philosophical pedigree back to Plato, and still plays a major role both in the epistemological analysis of knowledge (Lehrer, 1990; Leitgeb, 2014) and in accounts of rational belief change (Gärdenfors, 1988; Rott, 2005).

Within a topological framework for modeling inductive inference (Kelly, 1996; Schulte and Juhl, 1996; Martin et al., 2006; Yamamoto and de Brecht, 2010; Baltag et al., 2014b,a), we propose an explication of empirical simplicity inspired by Popper (2005). Ockham's vertical and horizontal razors require that one's belief state be, respectively, downward closed and co-initial in the simplicity order restricted to current information. We prove that, in the worst case, (i) Ockham's vertical razor is necessary for stable and for cycle-free convergence to the truth, and (ii) Ockham's horizontal razor is necessary for reversal minimal convergence to the truth.

### Lasha Abzianidze: A Logic of Belief with the Notion of Complexity

### A Logic of Belief with the Notion of Complexity

We present a logic of belief that takes into account a complexity of believing a sentence, namely, agents are better in believing sentences that are easily derivable from their initial belief set than in believing complex conclusions. It is shown that limited reasoning that is modeled in terms of complexities is sufficient for accounting for inconsistent beliefs and avoiding cases like omnidoxasticity and closure under (valid) implication. The logic also contains elements that are cognitively relevant.

### Leszek Wronski: Constraints on credences in two ...

### Constraints on credences in two not mutually exclusive propositions: the search for the best belief update function

Leitgeb and Pettigrew (2010) describe the following problem. Suppose an agent learns (only) that her new credences for propositions A and B should be p and q, respectively. What is the best rule of belief update, if A and B have a non-empty intersection? For Leitgeb and Pettigrew's sense of “best”, I present the best rule for the simplest non-trivial case of four possible worlds and show that it is not transferable to different cases. I show that the answer depends not only on the agent's initial credencies in A, B, and (A and B), but also on the cardinalities of the propositions.

10:00 - 11:15 | René Descartes Lecture II |
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Hannes Leitgeb (LMU Munich): Stability and Reasoning | |

11:15 - 11:45 | Coffee break |

11:45 - 13:00 | Commentaries by Nina Gierasimczuk (University of Amsterdam) and Jan-Willem Romeijn (RU Groningen) |

13:00 - 14:00 | Lunch Break |

14:00 - 16:00 | Contributed Talks (abstracts can be found below) |

Frederik Herzberg (Bielefeld University): A graded Bayesian coherence notion | |

Paul Thorn (Düsseldorf University): Another problem with deductive closure | |

Jan Sprenger (TiLPS): Hypothesis Acceptance and Degree of Corroboration | |

16:00 - 16:30 | Coffee Break |

16:30 - 17:50 | Contributed Talks (abstracts can be found below) |

Wolfgang Spohn (Konstanz University): The value of knowledge | |

Gerhard Schurz (Düsseldorf University): Impossibility results for stable rational belief | |

19:30 | Conference Dinner (Café Anvers) |

### Abstracts contributed talks Tuesday, 21 October

### Frederik Herzberg: A graded Bayesian coherence notion

### A graded Bayesian coherence notion

Coherence is a key concept in many accounts of epistemic justification within `traditional' analytic epistemology. Within formal epistemology, too, there is a substantial body of research on coherence measures. However, there has been surprisingly little interaction between the two bodies of literature.

The reason is that the existing formal literature on coherence measure operates with a notion of belief system that is very different from --- what we argue is --- a natural Bayesian formalisation of the concept of belief system from traditional epistemology. Therefore, formal epistemology has so far only been concerned with one particular --- arguably not even very natural --- way of formalising coherence of belief systems; it has by no means refuted the viability of coherentism. In contrast to the existing literature, we formalise belief systems as families of assignments of (conditional) degrees of belief (which may be compatible with several subjective probability measures).

Within this framework, we propose a Bayesian formalisation of the thrust of BonJour's coherence concept in "The structure of empirical knowledge" (1985), using a combination of Bayesian confirmation theory and basic graph theory. In excursions, we introduce graded notions for both logical and probabilistic consistency of belief systems --- the latter being based on certain geometrical structures induced by probabilistic belief systems.

For illustration, we reconsider BonJour's 'ravens' challenge (op. cit., p.95f.). Finally, potential objections to our proposed formal coherence notion are explored.

### Paul Thorn: Another problem with deductive closure

### Another problem with deductive closure

The present article illustrates a conflict between the claim that rational belief sets are closed under deductive consequences, and the claim that the relevant evidence bearing on a proposition is the sole determinant of whether it is rational to believe that proposition. Inasmuch as the latter claim is highly plausible, we have a strong reason to deny that rational belief sets are closed under deductive consequences.

### Wolfgang Spohn: The Value of Knowledge

### The Value of Knowledge

Usually, the value of true belief is discussed under this heading. I take this as sufficiently understood. In my talk I rather want to address the alleged surplus value of knowledge over true belief. Specifically, I want to interpret the familiar modal or counterfactual analyses of knowledge (sensitivity analysis, safety analysis) in terms of my ranking-theoretic account of counterfactuals. From there, I will derive that knowledge is stable true belief in a specific sense of stability. However, I do not offer this as an alternative account of knowledge, but as an explanation of its surplus value.

### Gerhard Schurz: Impossibility results for stable rational belief

### Impossibility results for stable rational belief

In this talk I show that certain rationality postulates for belief contradict each other. I consider the following postulates:

- Fallibilism (degrees of non-logically determined beliefs should be smaller than 1).
- Stability (in the sense as defined by Hannes Leitgeb).
- Semantic differentiation: Rational belief should be compatible with large propositional possibility spaces.
- Independence: Rational beliefs should be stable under expanding the possibility space by propositions which are probabilistically independent from these beliefs.

I will show that {1,2,3} and {1,2,4} are inconsistent. I will present some further impossibility theorems, explain their relation to the "preface paradox", and discusss their philosophical concequences concerning the following question: In which context should one give up which of these rationality postulates?

10:00 - 11:15 | René Descartes Lecture III |
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Hannes Leitgeb (LMU Munich): Stability and Action | |

11:15 - 11:45 | Coffee Break |

11:45 - 13:00 | Commentaries by Alexandru Baltag (University of Amsterdam) and Gerhard Schurz (Düsseldorf University) |

13:00 - 14:00 | Lunch Break |

14:00 - 16:00 | Contributed Talks (abstracts can be found below) |

Roger Clarke (Queen's University Belfast): Contrastive Belief, Full and Partial | |

Weng Hong Tang (National University of Singapore): Belief and Conditional Certainty | |

David Atkinson and Jeanne Peijnenburg (RU Groningen): Knowledge and Partial Knowledge | |

16:00 - 16:30 | Coffee Break |

16:30 - 18:00 | Final Session |

Branden Fitelson (Rutgers) compares Hannes Leitgeb's coherence requirements for (degrees of) belief to the requirements he develops in his own book | |

18:00 - 18:30 | Farewell Reception (Dante Building room DZ 5) |

### Abstracts contributed talks Wednesday, 22 October

### Roger Clarke: Contrastive Belief, Full and Partial

### Contrastive Belief, Full and Partial

Martijn Blaauw has recently advanced the provocative thesis that belief is essentially contrastive (Blaauw 2013). This thesis has been criticized by Baumann (2008, 2013) and Gerken and Beebe (forthcoming). I provide an alternative version of doxastic contrastivism, which better resists these criticisms. My contrastivism relies on the account of full and partial belief in Clarke (2013). That article claims, crucially to motivating doxastic contrastivism, that full and partial belief are both essentially sensitive to the space of alternative possibilities taken seriously by the believer in a given context; this space of alternatives provides the contrast in contrastive belief.

### Weng Hong Tang: Belief and Conditional Certainty

### Belief and Conditional Certainty

How is rational belief related to rational credence? In this paper, I'll defend the thesis that to rationally believe that p is to rationally assign a credence of 1 to p conditional on what is presupposed (where the relevant notion of presupposition will be spelt out in greater detail). The thesis, I'll argue, allows us to hold that we may rationally believe that p without assigning an unconditional credence of 1 to p. It also allows us to hold that rational beliefs are closed under entailment in every context (though not across contexts).

### David Atkinson & Jeanne Peijnenburg: Knowledge and Partial Knowledge

David Atkinson and Jeanne Peijnenburg

### Knowledge and Partial Knowledge

It is a platitude that belief comes in degrees, but the same cannot at all be said of knowledge: the received view is that knowledge is not gradable. Recently, however, some dissenting voices have been heard, claiming that knowledge might after all admit of a more or less. We add our voices to this chorus by generalizing the ideas of someone who does not believe that knowledge comes in degrees, namely Timothy Williamson.

In the language of possible worlds, knowledge has been defined by Williamson in terms of indiscriminability, conceived as a nontransitive accessibility relation that has sharp edges: a world w? is indiscriminable from world w, or it is not. A set of worlds, R, is known at w if R is true at all worlds that are accessible to w. We generalize Williamson's ideas by introducing the concept of partial knowledge, defined in terms of graded indiscriminability. This is seen as a probabilistic accessibility relation on a set of possible worlds, which has a model in a set of cloned worlds such that the strength of the accessibility of w? from w is proportional to the number of clones of w? that are accessible tout court, in the model, from w. An application of the mean-value theorem in the infinite limit motivates our adoption of a gaussian shape for the graded indiscriminability between possible worlds.

The method is illustrated by considering Williamson's modernist clock, which lacks all markings on its dial. Williamson's clock is intended to function as an exemplar of all cases in which knowledge is based upon indiscriminability. We show how to calculate the degree of partial knowledge of an agent concerning the interval in which the present time lies, conditioned on her being at a specified world. Finally, we explain how to compute the agent's partial knowledge, conditioned on her visual evidence (rather than on her being at a given world), with due account of her visual acuity. Partial knowledge goes over smoothly into full knowledge as the time-interval is made larger and larger. Williamson's categorical view of knowledge then serves as a limit case of our framework.