No Rationality Through Brute-Force

2010

Stalnaker provided an example of a perfect information game in which common knowledge of rationality does not yield backward induction. However, in his example, knowledge is treated as defeasible: players forfeit their knowledge of rationality at some vertices. This is not how ‘knowledge’ is understood in epistemology where, unlike belief, it is not subject to revision. In this respect, the Stalnaker example is a fit for ‘rationality and common belief of rationality’ rather than ‘common knowledge of rationality.’ In order to represent knowledge in the belief revision setting we introduce the notion of ‘robust knowledge’ which is maintained whenever possible during belief revision. We show that robust knowledge of Stalnaker rationality in games of perfect information yields backward induction.

2010

Stalnaker provided an example of a perfect information game in which common knowledge of rationality does not yield backward induction. However, in his example, knowledge is treated as defeasible: players forfeit their knowledge of rationality at some vertices. This is not how ‘knowledge’ is understood in epistemology where, unlike belief, it is not subject to revision. In this respect, the Stalnaker example is a fit for ‘rationality and common belief of rationality’ rather than ‘common knowledge of rationality.’ In order to represent knowledge in the belief revision setting we introduce the notion of ‘robust knowledge’ which is maintained whenever possible during belief revision. We show that robust knowledge of Stalnaker rationality in games of perfect information yields backward induction.

Many epistemologists equate the rational and the justied. Those who disagree have done little to explain the dierence, leading their opponents to suspect that the distinction is an ad hoc one designed to block counterexamples. The rst aim of this dissertationpursued in the rst three chaptersis to improve this situation by providing a detailed, independently motivated account of the distinction. The account is unusual in being inspired by no particular theoretical tradition in epistemology, but rather by ideas in the meta-ethical literature on reasons and rationality. The account is also unusual in proposing that the distinction between rationality and justication can be derived from a reasons-based account of justication. Historically, this is a striking claim. In epistemology, reasons-based accounts of justication are standardly treated as paradigmatically internalist accounts, but this dissertation argues that we should believe the reverse: given the best views about reasonsagain drawn from meta-ethicswe should expect reasons-based accounts of justication to be strongly externalist.

2021

The dominant theories of rational decision making assume what we will call logical omniscience. That is, they assume that when facing a decision problem, an agent can perform all relevant computations and determine the truth value of all relevant logical/mathematical claims. This assumption is unrealistic when, for example, we offer bets on remote digits of π or Goldbach’s conjecture; or when an agent faces a computationally intractable planning problem. Furthermore, the assumption of logical omniscience creates contradictions in cases where the environment can contain descriptions of the agent itself. Importantly, strategic interactions as studied in game theory are decision problems in which a rational agent is predicted by its environment (the other players). In this paper, we develop a theory of rational decision making that does not assume logical omniscience. We consider agents who repeatedly face decision problems (including ones like betting on Goldbach’s conjecture or games...

Philosophy, 1997

Are humans rational? In this new book, Edward Stein gives a clear account of the empirical and conceptual issues involved in settling this question, and in so doing draws certain conclusions regarding the naturalisation of epistemology. Stein distinguishes three senses of 'rational' in which we might be said to be rational. 1. We are rational in the sense that we think and reason, no matter how erroneously. 2. We are rational in the sense that we think and reason perfectly: all our beliefs are knowledge, all our deductions valid. Asserting 1. and denying 2. leaves open another sense in which we might be judged to be rational or irrational: 3. We are rational in the sense that whilst we sometimes make mistakes in our thinking and reasoning, these mistakes are always 'mere' mistakes.

Rough draft. To appear in Knauff, M. and Spohn, W. (ed.), Handbook of Rationality, MIT Press.

This chapter addresses the question as to how (if at all) propositional (PL) and first-order logic (FOL) relate to epistemic rationality. Rationality, it is often held, demands that our attitudes cohere in particular ways. Logic is often invoked as a source of such coherence requirements when it comes to belief: An ideally rational agent's beliefs are consistent and closed under logical consequence. However, this traditional picture has been challenged from various quarters. We begin by briefly reviewing the key concepts involved in PL and FOL. We then critically examine two distinct approaches to justifying logic-based requirements of rationality. The first lays down a set of desiderata codifying our intuitions, and then seeks to formulate a principle articulating the link between logic and rational belief that satisfies them. The second starts by identifying our most fundamental epistemic aim and seeks to derive requirements of rationality based on their ability to promote this aim.

Pacific Philosophical Quarterly, 2018

In this paper I deal with epistemological issues that stem from the hypothesis that reasoning is not only a means of transmitting knowledge from premise-beliefs to conclusion-beliefs, but also a primary source of knowledge in its own right. The idea is that one can gain new knowledge on the basis of suppositional reasoning. After making some preliminary distinctions, I argue that there are no good reasons to think that purported examples of knowledge grounded on pure reasoning are just examples of premise-based inferences in disguise. Next, I establish what kinds of true propositions can to a first approximation be known on the basis of pure reasoning. Finally, I argue that beliefs that are competently formed on the basis of suppositional reasoning satisfy both externalist and internalist criteria of justification.

1997

Synthese, 195: 491–510, 2018

ABSTRACT: The plausibility of so-called ‘rational explanations’ in cognitive science is often contested on the grounds of computational intractability. Some have argued that intractability is a pseudoproblem, however, because cognizers do not actually perform the rational calculations posited by rational models; rather, they only behave as if they do. Whether or not the problem of intractability is dissolved by this gambit critically depends, inter alia, on the semantics of the ‘as if’ connective. First, this paper examines the five most sensible explications in the literature, and concludes that none of them actually circumvents the problem. Hence, rational ‘as if’ explanations must obey the minimal computational constraint of tractability. Second, this paper describes how rational explanations could satisfy the tractability constraint. Our approach suggests a computationally unproblematic interpretation of ‘as if’ that is compatible with the original conception of rational analysis.

Frontiers in Psychology, 2014