This interdisciplinary work is a collection of major essays on reasoning: deductive, inductive, abductive, belief revision, defeasible (non-monotonic), cross cultural, conversational, and argumentative. They are each oriented toward contemporary empirical studies. The book focuses on foundational issues, including paradoxes, fallacies, and debates about the nature of rationality, the traditional modes of reasoning, as well as counterfactual and causal reasoning. It also includes chapters on the interface between reasoning and other forms of thought. In general, this last set of essays represents (...) growth points in reasoning research, drawing connections to pragmatics, cross-cultural studies, emotion and evolution. (shrink)

Knowledge can be transmitted by a valid deductive inference. If I know that p, and I know that if p then q, then I can infer that q, and I can thereby come to know that q. What feature of a valid deductive inference enables it to transmit knowledge? In some cases, it is a proof of validity that grounds the transmission of knowledge. If the subject can prove that her inference follows a valid rule, then her inference transmits knowledge. (...) However, this only pushes the question back to the inference that was made in this proof. What feature of that inference enables it to transmit knowledge? A vicious regress looms here. Every proof requires a valid inference, and every valid inference must follow at least one rule of inference. So every proof must follow at least one rule of inference. Therefore not every valid inference that transmits knowledge can acquire this power through a proof, on pain of vicious infinite regress. So it must be possible to transmit knowledge by making an inference that follows an underived rule. A deductive inference that follows an underived rule is what I will call a basic deductive inference. It must be possible to transmit knowledge by making a basic deductive inference. But how is this possible? What feature of a basic deductive inference gives it this power to transmit knowledge? (shrink)

Johnson-Laird's mental models theory claims that reasoning is a semantic process of construction and manipulation of models in working memory of limited capacity. Accordingly, both a deduction and a given interpretation of a premise would be all the harder the higher the number of models they require. The purpose of the present experiment was twofold. First, it aimed to demonstrate that the interpretation of if...then conditional sentences in children (third, sixth, and ninth graders) evolves as a function of the number (...) of models the children can produce. We proposed a theory of conditional reasoning development that hypothesises a developmental trend of three successive levels of interpretations underlain by one, two, and then three models, i.e. conjunctive, biconditional, and conditional respectively. Second, we aimed to show that these different levels correlate with working memory capacities: the higher the working memory span, the higher the number of models underlying the conditional interpretation. These two hypotheses were verified, supporting the mental models theory. The results are compared with the rival theory of mental logic. (shrink)

This paper attempts some integration of two perspectives on questions about rationality and irrationality: the classical conception of irrationality as sophism and themes from the romantic revolt against Enlightenment reason. However, since talk of "reason" and "the irrational" often invites rigid dualities of reason and its opposites (such as feeling, intuition, faith, or tradition), the paper turns to "intelligence" in place of "reason," thinking of human intelligence as something less abstract, less purely theoretical, and more firmly rooted in practice, including (...) communicative practice. "Intelligence" is "reason" naturalized. (shrink)

I consider backtracking reasoning: that is, reasoning from backtracking counterfactuals such as if Hitler had won the war, he would have invaded Russia six weeks earlier. Backtracking counterfactuals often strike us as true. Despite that, reasoning from them just as often strikes us as illegitimate. A number of diagnoses have been offered of the illegitimacy of such backtracking reasoning which invoke the fixity of the past, or the direction of causation. I argue against such diagnoses, and in favor of one (...) that invokes a principle I call the fixity of reasons. Backtracking reasoning violates the fixity of reasons. But, the fixity of reasons is a principle that must be observed in order to engage in practical reasoning at all. (shrink)

I pursue an answer to the psychological question “what is it for S to presuppose that p?” I will not attempt a general answer. Rather, I will explore a particular kind of presuppositions that are constituted by the mental act of reasoning: Inferential presuppositions. Indeed, I will consider a specific kind of inferential presuppositions—one that is constituted by a specific reasoning competence: The univocality competence. Roughly, this is the competence that reliably governs the univocal thought-components’ operation as univocal in a (...) line of reasoning. I will argue that the exercise of this reasoning competence constitutes certain inferential presuppositions. More specifically, I outline a conception of an inferential presupposition as a non-attitudinal but genuinely psychological and rationally committing relation that holds between a reasoner and a proposition. Thus, inferential presuppositions may be distinguished from tacit or standing attitudes that function as premise-beliefs in reasoning. Likewise inferential presuppositions may be distinguished from other kinds of presuppositions. In conclusion, I note some features of inferential presuppositions that bear on the epistemology of inference. (shrink)

In this paper, I challenge a widely presupposed principle in the epistemology of inference. The principle, (Validity Requirement), is this: S’s (purportedly deductive) reasoning, R, from warranted premise-beliefs provides (conditional) warrant for S’s belief in its conclusion only if R is valid. I argue against (Validity Requirement) from two prominent assumptions in the philosophy of mind: that the cognitive competencies that constitute reasoning are fallible, and that the attitudes operative in reasoning are anti-individualistically individuated. Indeed, my discussion will amount to (...) a defence of anti-individualism against a novel ‘slow-switch’ argument against it. This argument contra anti-individualism has it that given anti-individualism and certain auxiliary assumptions, A, a switched reasoner may, in certain slow-switch circumstances, C, reason invalidly by equivocating concepts. More specifically: (Valid 0): Peter is in circumstances C, and auxiliary assumptions, A, hold.(Valid 1): If Peter is in circumstances C, and auxiliary assumptions A hold, then (if the attitudes operative in Peter’s reasoning R are anti-individualistically individuated, then R is not valid). (Valid 2): Peter’s reasoning, R, generates warrant for the conclusion-belief. (Valid 3): Peter’s reasoning, R, generates warrant for the conclusion-belief only if the reasoning, R, is valid. (Valid 4): So, the attitudes operative in Peter’s reasoning R are not anti-individualistically individuated. The argument involves weaker premises than those of familiar slow-switch arguments against anti-individualism. In particular, it requires only that the reasoning be de facto valid. This assumption is much weaker than the requirement that the validity of the reasoning be ‘transparent’ to the reasoner. Indeed, (Valid 3) is simply an instance of (Validity Requirement). However, I argue that anti-individualism and (Valid 0)–(Valid 2) should be upheld at the expense of (Valid 3). In consequence, (Validity Requirement) stands in need of restriction. Thus, I argue for a surprising result in the epistemology of inference from widely accepted assumptions in the philosophy of mind. (shrink)

C hange in View offers an entirely original approach to the philosophical study of reasoning by identifying principles of reasoning with principles for revising one's beliefs and intentions and not with principles of logic. This crucial observation leads to a number of important and interesting consequences that impinge on psychology and artificial intelligence as well as on various branches of philosophy, from epistemology to ethics and action theory. Gilbert Harman is Professor of Philosophy at Princeton University. A Bradford Book.

Is it coherent to suppose that in order to hold a belief responsibly, one must recognize something else as a reason for it? This paper addresses this question by focusing on so-called “Inferential Internalist” principles, that is principles of the following form: in order for one to have positive epistemic status Ø in virtue of believing P on the basis of R, one must believe that R evidentially supports P, and one must have positive epistemic status Ø in relation to (...) that latter belief as well. While such principles and their close relatives figure centrally in a wide variety of recent epistemological discussions, there is confusion in the literature about what, precisely, Inferential Internalism commits one to and whether it is so much as coherent. This paper (1) articulates a broader framework for understanding the notion of epistemic responsibility, (2) motivates Inferential Internalism on the basis of considerations about the basing relation, epistemic responsibility, and parallels with practical deliberation, (3) defends Inferential Internalism against charges of incoherence leveled by James Van Cleve and Paul Boghossian, and (4) shows that contrary to a currently widespread view, Inferential Internalism is coherent even if foundationalism and the a priori are rejected. The paper closes with a preliminary argument for an affirmative answer to the initiating question about the requirements of epistemic responsibility. (shrink)

This book examines two questions: Do people make use of abstract rules such as logical and statistical rules when making inferences in everyday life? Can such abstract rules be changed by training? Contrary to the spirit of reductionist theories from behaviorism to connectionism, there is ample evidence that people do make use of abstract rules of inference -- including rules of logic, statistics, causal deduction, and cost-benefit analysis. Such rules, moreover, are easily alterable by instruction as it occurs in classrooms (...) and in brief laboratory training sessions. The fact that purely formal training can alter them and that those taught in one content domain can "escape" to a quite different domain for which they are also highly applicable shows that the rules are highly abstract. The major implication for cognitive science is that people are capable of operating with abstract rules even for concrete, mundane tasks; therefore, any realistic model of human inferential capacity must reflect this fact. The major implication for education is that people can be far more broadly influenced by training than is generally supposed. At high levels of formality and abstraction, relatively brief training can alter the nature of problem-solving for an infinite number of content domains. (shrink)

The paper argues that normative reasons are of two fundamental kinds, practical which are value related, and adaptive, which are not related to any value, but indicate how our beliefs and emotions should adjust to fit how things are in the world. The distinction is applied and defended, in part through an additional distinction between standard and non-standard reasons (for actions, intentions, emotions or belief).

Regress arguments seem to have convinced most philosophers that reasoning cannot require beliefs about what follows from what. In this paper I argue that this is a mistake. Regress arguments rest on dubious (although deeply entrenched) assumptions about the nature of reasoning — most prominently, the assumption that believing p by reasoning is simply a matter of having a belief in p with the right causal ancestry. I propose an alternative account, according to which beliefs about what follows from what (...) play a constitutive role in reasoning. As I argue, such beliefs are not exercises of any special-purpose faculty for detecting evidential relations. In the most basic cases, they arise from exercises of our capacity for self-knowledge. (shrink)

What exactly is reasoning? Like many other philosophers, I shall endorse a broadly causal conception of reasoning. Reasoning is a causal process, in which one mental event (say, one’s accepting the conclusion of a certain argument) is caused by an antecedent mental event (say, one’s considering the premises of the argument). Just like causal accounts of action and causal accounts of perception, causal accounts of reasoning have to confront a version of what has come to be known as the problem (...) of deviant causal chains. In this paper, I shall propose an account of the nature of reasoning, incorporating a solution to the specific version of the deviant causal chains problem that arises for accounts of reasoning. One striking feature of my solution is that it requires that certain normative facts are causally efficacious. It might be thought that this feature will make my account incompatible with any plausibly naturalistic approach to understanding the mind. I shall argue that this is not so: my account of the nature of reasoning is quite compatible with plausible versions of naturalism. (shrink)

It has been a commonplace from the beginnings of philosophical thought that what distinguishes humans from other species is the ability to reason; reason- ing is held to be an essential characteristic of the species and one that is unique to it. The essence condition requires that all humans possess at least the capacity for reasoning and that it be exercised in many of the ordinary cases of acquiring beliefs. And uniqueness entails that non-humans cannot reason, no matter how much (...) their behavior resembles that of humans. I think that a certain specific model of reasoning has been presupposed by proponents of these claims. And there are grounds to believe that this model is inaccurate in essential respects: if reasoning does correspond to it, then few human beliefs are acquired through reason. However, given a more accurate description of what goes on in normal human reasoning, it is no longer plausible to think that only humans reason. So either the essence or the uniqueness claim must be given up. In this paper I argue for the second option. (shrink)