My work in decision theory and practical rationality deals with the question of what rationality demands when choices are made both over time and in the context of uncertainty. I have worked on the adequacy of alternatives to expected utility theory in temporally extended choice contexts. And my PhD dissertation argues that the core requirements of standard expected utility theory are requirements of instrumental rationality only for agents who desire to have stable choice dispositions over time.

In ethics, I have published on social contract theory. I am particularly interested in the use of game theory when it comes to determining the terms of the social contract. In philosophy of science, I have been concerned with the social structure of science. I have programmed an agent-based model to study the epistemic benefits from division of labour in science using Netlogo. And I have worked on the methodological question of what idealised models can teach us about the world.

Work in Progress:

Preference Cycles and the Requirements of Instrumental Rationality

Abstract: Many decision theorists take standard normative decision theory to be a theory of instrumental rationality, and its core requirements to be requirements of instrumental rationality. This paper argues that at least one such core requirement, namely the acyclicity of preference, cannot be defended as a general requirement of instrumental rationality. The standard instrumentalist defence of the requirement to have acyclical preferences, the Money Pump Argument, relies on a fatal equivocation about the standard of instrumental rationality. If the fundamental conative attitudes against which our actions are evaluated are attitudes to the fully described outcomes of our actions, we cannot show that being money pumped is instrumentally irrational. If, however, the standard of instrumental rationality are attitudes to features of the outcomes of our actions, we cannot show that instrumentally rational agents must adopt acyclical preferences to avoid being money pumped.

Instrumental Rationality Without Separability

Abstract: This paper argues that instrumental rationality is more permissive than expected utility theory. The most compelling instrumentalist argument in favour of separability, its core requirement, is that agents with non-separable preferences end up badly off by their own lights in some dynamic choice problems. I argue that once we focus on the question of whether agents’ attitudes to uncertain prospects help define their ends in their own right, or instead only assign instrumental value in virtue of the outcomes they may lead to, we see that the argument must fail. Either attitudes to prospects assign non-instrumental value in their own right, in which case we cannot establish the irrationality of the dynamic choice behaviour of agents with non-separable preferences. Or they don’t, in which case agents with non-separable preferences can avoid the problematic choice behaviour without adopting separable preferences.

Temptation and Preference-Based Instrumental Rationality

Abstract: In the dynamic choice literature, temptations are usually understood as temporary shifts in an agent’s preferences. What has been puzzling about these cases is that, on the one hand, an agent seems to do better by her own lights if she does not give into the temptation, and does so without engaging in costly commitment strategies. This seems to indicate that it is instrumentally irrational for her to give into temptation. On the other hand, resisting temptation also requires her to act contrary to the preferences she has at the time of temptation. But that seems to be instrumentally irrational as well. I here consider the two most prominent types of argument why resisting temptation could nevertheless be instrumentally rational, namely two-tier and intra-personal cooperation arguments. I establish that the arguments either fail or are redundant. In particular, the arguments fail under the pervasive assumption in both decision theory and the wider literature on practical rationality that the agent’s preferences over the objects of choice are themselves the standard of instrumental rationality. And they either still fail or they become redundant when we give up that assumption.

Risk Aversion and the Long Run

Abstract: The counter-examples to expected utility theory that motivate alternative theories of rational choice are usually presented as one-off choices, isolated from the agent’s wider choice context. However, any real agent faces many decisions involving uncertainty in her life. This fact raises deep problems for alternatives to expected utility theory. This paper argues that one prominent alternative theory of instrumentally rational choice, rank-dependent utility theory in the form of Buchak’s (2013) risk-weighted expected utility (REU) theory, ultimately fails to offer a real alternative to expected utility theory. Under plausible and commonly held assumptions about dynamic choice and the framing of decision problems, rational agents will be guided by their attitudes to entire courses of action over time. And then REU theory ends up making approximately the same recommendations as expected utility theory. Yet being more permissive about dynamic choice or the framing of decision problems undermines the theory’s claim to capturing a stable choice disposition in the face of risk, and thus its purpose as a normative and explanatory theory of choice under uncertainty. I argue that this in fact poses a challenge to alternatives to expected utility theory more generally.

Published Papers:

Risk Writ Large (with Jonathan Weisberg) in Philosophical Studies 174 (9), pp. 2369–2384, 2017. 

Abstract: Risk-weighted expected utility (REU) theory is motivated by small-world problems like the Allais paradox, but it is a grand-world theory by nature. And, at the grand-world level, its ability to handle the Allais paradox is dubious. The REU model described in Risk & Rationality turns out to be risk-seeking rather than risk-averse on one natural way of formulating the Allais gambles in the grand-world context. This result illustrates a general problem with the case for REU theory, we argue. There is a tension between the small-world thinking marshaled against standard expected utility theory, and the grand-world thinking inherent to the risk-weighted alternative.

Lara Buchak responds here, to which we responded here.

On the Hidden Thought Experiments of Economic Theory (2016) in Philosophy of the Social Sciences 46 (2), pp. 129-146.

Abstract: Most papers in theoretical economics contain thought experiments. They take the form of more informal bits of reasoning that precede the presentation of the formal, mathematical models these papers are known for. These thought experiments differ from the formal models in various ways. In particular, they do not invoke the same idealized assumptions about the rationality, knowledge and preferences of agents. The presence of thought experiments in papers that present formal models, and the fact that they differ from the formal models in this way are often ignored in debates on what, if anything, we can learn from formal models in theoretical economics. I show that paying due attention to thought experiments in theoretical economics has serious implications for this debate. Differences between thought experiments and formal models are especially problematic for Sugden’s ‘credible worlds’ account.

Bargaining and the Impartiality of the Social Contract (2015) in Philosophical Studies 172 (12), pp. 3335-3355.

Abstract: The question of what a group of rational agents would agree on were they to deliberate on how to organise society is central to all hypothetical social contract theories. If morality is to be based on a social contract, we need to know the terms of this contract. One type of social contract theory, contractarianism, aims to derive morality from rationality alone. Contractarians need to show, amongst other things, that rational and self-interested individuals would agree on an impartial division of a cooperative surplus. But it is often claimed that contractarians cannot show this without introducing moral assumptions. This paper argues that on the right understanding of the question contractarians are asking, these worries can be answered. Without relying on moral assumptions, the paper offers a novel derivation of symmetry, which is the axiom responsible for the impartiality of the most famous economic bargaining solutions appealed to by contractarians.

The Epistemic Division of Labor Revisited (2015) in Philosophy of Science 82 (3), pp. 454-472. (programmed with Netlogo)

Abstract: Some scientists are happy to follow in the footsteps of others; some like to explore novel approaches. It is tempting to think that herein lies an epistemic division of labor conducive to overall scientific progress: the latter point the way to fruitful areas of research, and the former more fully explore those areas. Weisberg and Muldoon’s model, however, suggests that it would be best if all scientists explored novel approaches. I argue that this is due to implausible modeling choices, and I present an alternative ‘epistemic landscape’ model that demonstrates the alleged benefits from division of labor, with one restriction.