This essay argues that when setting climate policy, we should place more weight on worse possible consequences of a policy, while still placing some weight on better possible consequences. The argument proceeds by elucidating the range of attitudes people can take towards risk, how we must make choices for people when we don't know their risk-attitudes, and the situation we are in with respect to climate policy and the consequences for future people. The result is an alternative to the Precautionary Principle, an alternative that gives similar policy recommendations in many cases but is also sensitive to the costs of precautions.

My book Risk and Rationality argues for a new alternative to the orthodox theory of rational decision-making. This alternative, risk-weighted expected utility maximization, holds that there are three important components involved in rational decision-making: utilities, probabilities, and risk-attitudes. This essay explains the basic outline of the theory and precisely how it differs from the orthodox theory. It also summarizes the main threads of argument in the book.

There are currently two robust traditions in philosophy dealing with doxastic attitudes: the tradition that is concerned primarily with all-or-nothing belief, and the tradition that is concerned primarily with degree of belief or credence. This paper concerns the relationship between belief and credence for a rational agent, and is directed at those who may have hoped that the notion of belief can either be reduced to credence or eliminated altogether when characterizing the norms governing ideally rational agents. It presents a puzzle which lends support to two theses. First, that there is no formal reduction of a rational agent's beliefs to her credences, because belief and credence are each responsive to different features of a body of evidence. Second, that if our traditional understanding of our practices of holding each other responsible is correct, then belief has a distinctive role to play, even for ideally rational agents, that cannot be played by credence. The question of which avenues remain for the credence-only theorist is considered. © 2013 Springer Science+Business Media Dordrecht.

A natural view in distributive ethics is that everyone’s interests matter, but the interests of the relatively worse off matter more than the interests of the relatively better off. I provide a new argument for this view. The argument takes as its starting point the proposal, due to Harsanyi and Rawls, that facts about distributive ethics are discerned from individual preferences in the “original position.” I draw on recent work in decision theory, along with an intuitive principle about risk taking, to derive the view.

It is sometimes said that faith is recalcitrant in the face of new evidence, but it is puzzling how such recalcitrance could be rational or laudable. I explain this aspect of faith and why faith is not only rational, but in addition serves an important purpose in human life. Because faith requires maintaining a commitment to act on the claim one has faith in, even in the face of counter-evidence, faith allows us to carry out long-term, risky projects that we might otherwise abandon. Thus, faith allows us to maintain integrity over time.

Some early phase clinical studies of candidate HIV cure and remission interventions appear to have adverse medical risk-benefit ratios for participants. Why, then, do people participate? And is it ethically permissible to allow them to participate? Recent work in decision theory sheds light on both of these questions, by casting doubt on the idea that rational individuals prefer choices that maximise expected utility, and therefore by casting doubt on the idea that researchers have an ethical obligation not to enrol participants in studies with high risk-benefit ratios. This work supports the view that researchers should instead defer to the considered preferences of the participants themselves. This essay briefly explains this recent work, and then explores its application to these two questions in more detail.

The orthodox theory of instrumental rationality, expected utility (EU) theory, severely restricts the way in which risk-considerations can figure into a rational individual's preferences. It is argued here that this is because EU theory neglects an important component of instrumental rationality. This paper presents a more general theory of decision‐making, risk-weighted expected utility (REU) theory, of which expected utility maximization is a special case. According to REU theory, the weight that each outcome gets in decision‐making is not the subjective probability of that outcome; rather, the weight each outcome gets depends on both its subjective probability and its position in the gamble. Furthermore, the individual's utility function, her subjective probability function, and a function that measures her attitude towards risk can be separately derived from her preferences via a Representation Theorem. This theorem illuminates the role that each of these entities plays in preferences, and shows how REU theory explicates the components of instrumental rationality.

I have claimed that risk-weighted expected utility (REU) maximizers are rational, and that their preferences cannot be captured by expected utility (EU) theory. Richard Pettigrew and Rachael Briggs have recently challenged these claims. Both authors argue that only EU-maximizers are rational. In addition, Pettigrew argues that the preferences of REU-maximizers can indeed be captured by EU theory, and Briggs argues that REU-maximizers lose a valuable tool for simplifying their decision problems. I hold that their arguments do not succeed and that my original claims still stand. However, their arguments do highlight some costs of REU theory.

I reply to two commentaries—one by Johanna Thoma and Jonathan Weisberg and one by James M. Joyce—concerning how risk-weighted expected utility theory handles the Allais preferences and Dutch books.

John Broome has argued that there are distinct requirements of rationality and reason. Niko Kolodny has defended an error theory about requirements of rationality, arguing that requirements of rationality fall out of the requirements of reason, not in the straightforward sense that one has a reason to be rational as such, but in the sense that requirements of rationality are a byproduct of requirements of reason. Recent work in the theory of group agency and the problem of judgment aggregation raises a difficulty for applying Kolodny's error theory to the case of requirements of group rationality and group reason. This chapter explores ways in which the conflict between the proposed error theory in the group case and the results concerning judgment aggregation might be resolved. The chapter also considers what bearing the group case has on the success of the error theory in the individual case.