# Abstracts

### Rutgers Conference on the Philosophy of Probability

#### October 24-26, 2019

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Ned Hall, “Humean revisionism about chance”

The substantial literature on the Humean/anti-Humean divide about the physical modalities (laws, causation, and chance) has not, I think, fully appreciated how consequential that choice is, for our understanding of objective probability. I’ll attempt to draw attention to some of the most interesting revisionary consequences of one important Humean approach: the “best system” approach championed by Lewis, Beebee, and others. I say “revisionary”, because to the extent that we share a pre-theoretical, intuitive understanding of chance, that understanding is, I think, best captured by an anti-Humean conception. That said, the point here is not to argue for such a conception (after all, who says that chances have to fit our intuitive understanding of them?); rather, my hope is to clarify the stakes.

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Katie Elliott, “Chance Explanation”

When an event occurs by chance, what explains the event’s occurrence? According to traditional views, a chance event’s occurrence is explained by something other than, or something more than, the event’s chance of occurring, such as conditions that obtain prior to the event’s occurrence, the event’s causes, or the laws governing the event’s occurrence.

I present a rival picture of chance explanation on which the explanatory contribution of antecedent conditions, causes, and natural laws is always mediated by the event’s chance of occurring, e.g., the present chances explain future occurrences, while the present conditions, causes, and natural laws help to explain the present chances. I argue that this picture has two interesting theoretical advantages.

First, chance is a kind of predictive choke point between the past and the future. There is a great deal of evidence that one might presently have about whether a particular event will occur in the future, but the event’s chance of occurring is at least as good grounds for one’s expectations about whether the event occurs in the future as is (nearly) all of that other evidence. I show how to account for this aspect of chance’s predictive role with my picture of chance’s explanatory role.

Second, there is a question about whether there can be chances in deterministic worlds or whether there can be autonomous chances at work in macrophysical processes. I show that my picture of chance’s explanatory role lights the way toward progress on this rather abstract metaphysical question by reducing it to (what I take to be) more tractable questions about the explanatory power of scientific theories.

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Christopher Meacham, “What a non-Humean Lewisian should say about laws and chance”

Non-Humean accounts of laws and chance tend to face the following problem regarding statistical mechanical chances: either they are unable to accommodate statistical mechanical chances, or they do so in a way that is underspecified or underconstrained. In this talk I aim to sketch a non-Humean account of laws and chances that can accommodate statistical mechanical chances and avoids these demerits. Taking Lewis’s metaphysical framework as a starting point, I suggest that we postulate a single fundamental nomic relation. I then present representation and uniqueness theorems showing how one can provide an account of laws and chances in terms of this relation that is fully specified and appropriately constrained. Finally, I sketch a couple interesting consequences of this account in the context of Lewis’s framework, and note at least one revision to Lewis’s metaphysical picture which this account suggests; a revision which, in retrospect, we should have wanted all along.

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Carl Hoefer, “How *a priori* should the chances be in Statistical Mechanics?”

In my talk I will compare and contrast the Humean approach to SM chances advocated in Frigg & Hoefer (2013) and Hoefer (2019) with the alternative approaches of Myrvold (2012), Loewer & Albert (in diverse publications), and Hemmo & Shenker (2012). While all these approaches agree in maintaining that the probabilities of SM can be both *objective* (in at least some significant sense) and compatible with underlying determinism, they disagree on what actually determines the values of the probabilities. I will defend the need to blend both “*a priori*” and empircal/actual-fact elements in the recipe that determines the probabilities, and to do so in a way that gives the latter element a strong role.

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Wayne Myrvold, “Beyond Chance and Credence”

It has long been recognized that the word “probability” is used in (at least) two distinct senses: an epistemic notion, having to do with degrees of belief of an agent with less than complete information about the world, and objective chance, which is meant to be a feature of the physical world, entirely independent of considerations of such agents. I will argue that this familiar dichotomy is insufficient, and that there is a role to play for a hybrid concept, that combines physical and epistemic considerations, which I call “epistemic chance.”

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Richard Pettigrew, “What accuracy can teach us about chance-credence principles”

Chance-credence principles tell us how our beliefs about the objective chances should relate to our beliefs about other things. Roughly speaking, things we believe to have a higher chance of happening we should believe more strongly. But we need something more precise than this. However, when we come to formulate the principles with full precision, a range of different possibilities present themselves: Lewis’s Principal Principle, Hall’s New Principle, and Ismael’s General Recipe, to name a few. Yet each of these faces various problems, particularly if our metaphysics of chance allows so-called self-undermining chances. How are we to adjudicate between these? In this talk, I’ll appeal to accuracy-first epistemology to determine which chance-credence principle we should use.

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Jack Spencer, “How (Not) to Justify Chance-Credence Norms”

*This is joint work with David Builes (MIT)*

This paper is partly about how to justify chance-credence norms. We defend a theory of chancemaking that, together with a thesis about the *a priori* status of truths about rationality, entails a wide variety of chance-credence norms. But this paper is also partly about some beliefs about chance-credence norms that we think are mistaken. Chief among them is the assumption that chance-credence norms are *additional* constraints on rational credence. Let the *nonchancy constraints* be the constraints on rational credence, besides the ones imposed by chance-credence norms. Chance-credence norms are additional constraints if a credence function could satisfy the nonchancy constraints yet violate a chance-credence norm. We deny that chance-credence norms are additional constraints, and we draw out some of the interesting consequences of denying that chance-credence are additional constraints.

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Valia Allori, “Typicality, Probability, and Explanation”

A common way of characterizing Boltzmann’s explanation of thermodynamics in term of statistical mechanics is with reference to three ingredients: the dynamics, the past hypothesis, and the statistical postulate. In this paper I focus on the statistical postulate, and I have three aims. First, I wish to argue that regarding the statistical postulate as a probability postulate is too strong: a postulate about typicality would be enough. Second, I show that there is no need to postulate anything, for the typicality postulate can be suitably derived from the dynamics. Finally, I discuss how the attempts to give preference to certain stochastic quantum theories (such as the spontaneous collapse theory) over deterministic alternatives on the basis that they do not need the statistical postulate fail.

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