Review of Time Biases: A Theory of Rational Planning and Personal Persistence by Meghan Sullivan Published in the Journal of Moral Philosophy (2020) Reviewer: Travis Timmerman, Seton Hall University Biases are generally regarded as bad, and people typically try to weed their biases out, except perhaps, when it comes to temporal biases. Temporal biases are systematic preferences about when good and bad events occur, and most people have deep seated temporal biases. More specifically, most people are near biased and future biased. In loose terms, near biased people prefer to have some lesser good in the near future over some greater good in the more distant future and some greater bad in the distant future over some lesser bad in the near future. For instance, many people will prefer a three hour colonoscopy in eighteen months over a two hour colonoscopy today, even though this seems to be the prudentially worst outcome (p. 14). Even more people are future biased, preferring to have a greater painful experience in the past over a less painful experience in the near future. Recall Parfit's famous My Past or Future Operations Case (Parfit 1984, pp. 165-166). You wake up in the hospital and are told that you either underwent an excruciatingly painful surgery without anesthesia for ten hours (followed by an amnesia drug) or will undergo an excruciatingly painful surgery for one hour (followed by an amnesia drug). Most prefer to have the surgery over and done with, even though this seems to be a preference for the prudentially worst outcome. In her exceptional new book Time Biases: A Theory of Rational Planning and Personal Persistence, Meghan Sullivan aims to demonstrate that temporal bias is irrational and that we instead should be temporally neutral. That is, ceteris paribus, we should be indifferent to when good and bad events occur. The book is divided into eleven chapters. The first chapter lays the groundwork for the book, introducing the reader to the relevant concepts through a mix of illuminating personal anecdotes, review of relevant psychological literature, and compelling thought experiments. In chapters two and three, Sullivan makes her case against the rationality of near bias, which primarily revolve around the following two arguments. The Life-Saving Argument for Future Neutrality (1) At any given time, a rational agent prefers that her life going forward go as well as possible. (The Success Principle) (2) If you are near-biased, then in distant tradeoffs you will prefer and choose the present, lesser good over the greater, future good. (3) Your life going forward would go better if you preferred and chose the greater, future good in a distant tradeoff. (4) Therefore, near-biased preferences are not rationally permissible, insofar as you face a distant tradeoff choice (pp. 22-23). The Arbitrariness Argument for Future Neutrality (1) At any given time, a prudentially rational agent's preferences are insensitive to arbitrary differences. (The Non-Arbitrariness principle) (2) Relative distance from the present is an arbitrary difference between events. (3) If you are near-biased, your preferences are sensitive to when an event is scheduled relative to the present. (4) So, at any given time, near-biased preferences are not rationally permissible (pp. 36-37). Sullivan's central arguments against time bias in its various forms appeal to The Success Principle, The Non-Arbitrariness Principle, and the soon-to-be-discussed Weak Forecasting principle. After reviewing and rebutting a number of objections to the aforementioned arguments, Sullivan turns to considerations of personal volatility (i.e. how individuals vary over time, both in their personality traits and in terms of personal identity) in chapter four. Sullivan argues that neither kind of personal volatility justifies temporal bias. Sullivan then turns her attention to future bias in chapter five, reviewing the psychological literature establishing that people are future biased, and the seminal philosophical literature on the topic. This makes way for her arguments against future bias in chapters six and seven. Her central arguments against future bias invoke a principle Sullivan refers to as Weak Forecasting. Weak Forecasting: If you have and always will have all of the relevant information about the options available to you, then it is permissible for you to prefer any option you know you will never regret in favor of one you know you will eventually regret (p. 95). Here is Sullivan's primary concern. If people are future biased and Weak Forecasting is true, then they will be rationally permitted to choose lesser goods in the future over greater goods in the ever-so-slightly later future. Such choices seem irrational, so future bias must be irrational. To illustrate the issue, suppose that at t1 , an agent knows that they will have the option to enjoy two cookies at t3 or one cookie at t5. Since they are (absolutely) future biased, they know that if they choose two cookies at t3, they would regret this decision at t4, wishing (at that time) that they would instead get a single cookie in the near future at t5. Given Weak Forecasting, the agent is then rationally permitted to choose one cookie at t5 over two at t3. But this seems irrational, as that results in the agent getting the least amount of good! This is an interesting argument, and I agree that it would be irrational to choose the lesser good in these sorts of case. Since future bias and Weak Forecasting entail that such choices are rationally permissible, either future bias is unjustified or Weak Forecasting is false. Sullivan takes the culprit to be future bias, though I worry that the culprit may be Weak Forecasting. Weak Forecasting seems to permit paradigmatically irrational actions by allowing agents to perform actions that will make them worse off in the long run. To see why, suppose that you have the following two options available to you. A would bring you eleven units of goodness and one unit of pain. You would briefly regret choosing this option during the moment you feel the pain and then cease to regret it after the fact. B would bring you five units of goodness and zero units of pain. You would never regret choosing this option. Between these options, choosing B seems clearly irrational, while choosing A seems rationally obligatory.1 Now, suppose that the agent is aware of all of the relevant information about the options available to them and, all else equal, actually prefers A. But, following Weak Forecasting, opts for B. Weak Forecasting seems to entail that this is rationally permissible and that seems wrong. More generally, Weak Forecasting seems to entail that it can be prudentially rationally permissible to select the prudentially worst option for a person, even holding fixed the temporal location of events. If this is right, then there is good reason to doubt Weak Forecasting and, consequently, we should be less confident that future bias is irrational. Perhaps Sullivan could respond by holding that it is always prudentially irrational to prefer that one gets the lesser amount of net good. While this seems like a plausible principle, at least in the abstract, it would immediately rule out the rationality of temporal bias and, as such, would be question-begging if it were underlying arguments against temporal bias.2 Though, perhaps Sullivan need only combine Weak Forecasting with the weaker, forward looking, Success Principle in order to avoid counterintuitive conclusions in my example. This move raises another worry, however. If agents are always prudentially rationally required to prefer the greater good in the future, and if Sullivan weakens Weak Forecasting by denying that it applies to cases where agents would regret choosing the greater good, then Weak Forecasting is rendered moot. The Success Principle would be doing all the necessary work in the arguments against future bias, while Weak Forecasting would become completely superfluous. Even if I am right about this problem, it won't be much comfort to defenders of temporal bias. Sullivan's arguments against the rationality of future bias that do not rely on Weak Forecasting (e.g. that it allows agents to be money pumped) may be sound, and there may even be some way to tweak Weak Forecasting to avoid the issue I raise here. In chapter eight, Sullivan lays out what temporal neutrality does, and doesn't, require of agents, allowing that agents can take their (non-rational) emotional responses into account when deciding how to act. She also reviews a possible evolutionary explanation for temporal bias, as well as interesting empirical studies concerning self/other asymmetries in temporal bias. People tend not to be future biased about others' situations, even though they are future biased about their own. Chapter nine explores the relationship between temporal neutrality and sunk cost reasoning, and Sullivan develops a principled means of distinguishing between fallacious sunk cost reasoning and rationally permissible deference to past plans. 1 If both choices seem on a par, then just increase the difference in net goodness between A and B to the extent necessary to make choosing B irrational. The same point may be illustrated with cases where only different quantities of pleasure are at stake. Still, I see no reason why the mere fact that one might regret choosing the greater quantity of pleasure makes it rationally permissible to choose the lesser quantity of pleasure. 2 Alternatively, Sullivan could bite the bullet and appeal to some account of desire satisfactionism that might permit such judgments. This would, however, significantly narrow the scope of Sullivan's argument by restricting it to certain desire satisficationists who are inclined to accept temporal bias. Moreover, it would create a tension with her arguments against temporal bias. If it is rationally permissible to desire the lesser good in cases like the one above, then why isn't it also rationally permissible to desire the lesser good in cases of temporal bias? This response, then, is one that I think Sullivan is unlikely to endorse. Chapter ten primarily revolves around the question of when the temporally neutral agent should prefer an afterlife to annihilation. Appealing to a modified Weak Forecasting principle, Sullivan argues that an agent can rationally choose eternal life if they will always affirm (or be indifferent to) the afterlife in question over its alternative of non-existence (p. 161). Chapter eleven focuses on an argument for temporal nihilism, which entails that there is no point to doing anything that won't make a permanent difference. Sullivan makes a compelling case that rejecting future bias in favor of temporal neutrality allows one to avoid this argument for temporal nihilism by positing the right kind of "connection facts" between various events to ground meaning. Such facts can connect to past events, as well as future events. The rich and illuminating discussion surrounding these varied and complex issues will be of special interest to those who work in the philosophy of death literature. The best books in philosophy focus on a new (or underexplored) problems and make significant headway in solving those problems. Sullivan's Time Biases does exactly that. Her arguments are original, insightful, and usually compelling. Her understanding of the issues are so deep, and her writing so clear, that the careful reader can't help but gain a significant understanding of the relevant philosophical terrain. This book is an invaluable contribution to the literature on time biases, which will hopefully grow in the future, thanks in part to this groundbreaking work. References Parfit, Derek. Reasons and Persons (Oxford; New York, 1984). Sullivan, Meghan. Time Biases: A Theory of Rational Planning and Personal Persistence. (Oxford; New York, 2018).