There was a long tradition in philosophy according to which good reasoning had to be deductively valid. However, that tradition began to be questioned in the 1960’s, and is now thoroughly discredited. What caused its downfall was the recognition that many familiar kinds of reasoning are not deductively valid, but clearly confer justification on their conclusions. Here are some simple examples.

One of Hume's most well-known works and a masterpiece of philosophy, A Treatise of Human Nature is indubitably worth taking the time to read.

According to Aristotle, humans are the rational animal. The borderline between rationality and irrationality is fundamental to many aspects of human life including the law, mental health, and language interpretation. But what is it to be rational? One answer, deeply embedded in the Western intellectual tradition since ancient Greece, is that rationality concerns reasoning according to the rules of logic – the formal theory that specifies the inferential connections that hold with certainty between propositions. Piaget viewed logical reasoning as defining (...) the end-point of cognitive development; and contemporary psychology of reasoning has focussed on comparing human reasoning against logical standards. (shrink)

It ‘seems altogether inconceivable', says Hume, that this ‘new relation' ought ‘can be a deduction' from others ‘which are entirely different from it' The idea that you can't derive an Ought from an Is, moral conclusions from non-moral premises, has proved enormously influential. But what did Hume mean by this famous dictum? Was he correct? How does it fit in with the rest of his philosophy? And what does this suggest about the nature of moral judgements? This collection, the first (...) on this topic for forty years, assembles a distinguished cast of international scholars to discuss these questions. The book combines, historical scholarship, meta-ethics and cutting-edge research in philosophical logic. It includes three distinct attempts to reformulate and prove No-Ought-From-Is in the face of Prior's famous counterexamples. -/- Contributors: A.N. Prior, Gerhard Schurz, Charles Pigden, J.M.Shorter, Annette.C.Baier, Wade Robison, Adrian Heathcote, Alan Musgrave, Norva Y.S. Lo, Gillian Russell, Hakan Salwén, Greg Restall, Peter Vranas, Edwin Mares, Stephen Maitzen. (shrink)

In this response, we clarify several misunderstandings of the understanding/acceptance principle and defend our specific operationalization of that principle. We reiterate the importance of addressing the problem of rational task construal and we elaborate the notion of computational limitations contained in our target article. Our concept of thinking dispositions as variable intentional-level styles of epistemic and behavioral regulation is explained, as is its relation to the rationality debate. Many of the suggestions of the commentators for elaborating two-process models are easily (...) integrated into our generic dual-process account. We further explicate how we view the relation between System 1 and System 2 and evolutionary and normative rationality. We clarify our attempt to fuse the contributions of the cognitive ecologists with the insights of the original heuristics and biases researchers. (shrink)

David and Mary Norton present the definitive scholarly edition of Hume's Treatise, one of the greatest philosophical works ever written. This set comprises the two volumes of texts and editorial material, which are also available for purchase separately. David Hume is one of the greatest of philosophers. Today he probably ranks highest of all British philosophers in terms of influence and philosophical standing. His philosophical work ranges across morals, the mind, metaphysics, epistemology, religion, and aesthetics; he had broad interests not (...) only in philosophy as it is now conceived but in history, politics, economics, religion, and the arts. He was a master of English prose. The Clarendon Hume Edition will include all of his works except his History of England and minor historical writings. It is the only thorough critical edition, and will provide a far more extensive scholarly treatment than any previous editions. This edition offers authoritative annotation, bibliographical information, and indexes, and draws upon the major advances in textual scholarship that have been made since the publication of earlier editions - advances both in the understanding of editorial principle and practice and in knowledge of the history of Hume's own texts. (shrink)

Mere facts about how the world is cannot determine how we ought to think or behave. Elqayam & Evans (E&E) argue that this undercuts the use of rational analysis in explaining how people reason, by ourselves and with others. But this presumed application of the fallacy is itself fallacious. Rational analysis seeks to explain how people do reason, for example in laboratory experiments, not how they ought to reason. Thus, no ought is derived from an is; and rational analysis is (...) unchallenged by E&E's arguments. (shrink)

We propose a critique ofnormativism, defined as the idea that human thinking reflects a normative system against which it should be measured and judged. We analyze the methodological problems associated with normativism, proposing that it invites the controversial “is-ought” inference, much contested in the philosophical literature. This problem is triggered when there are competing normative accounts (the arbitration problem), as empirical evidence can help arbitrate between descriptive theories, but not between normative systems. Drawing on linguistics as a model, we propose (...) that a clear distinction between normative systems and competence theories is essential, arguing that equating them invites an “is-ought” inference: to wit, supporting normative “ought” theories with empirical “is” evidence. We analyze in detail two research programmes with normativist features – Oaksford and Chater's rational analysis and Stanovich and West's individual differences approach – demonstrating how, in each case, equating norm and competence leads to an is-ought inference. Normativism triggers a host of research biases in the psychology of reasoning and decision making: focusing on untrained participants and novel problems, analyzing psychological processes in terms of their normative correlates, and neglecting philosophically significant paradigms when they do not supply clear standards for normative judgement. For example, in a dual-process framework, normativism can lead to a fallacious “ought-is” inference, in which normative responses are taken as diagnostic of analytic reasoning. We propose that little can be gained from normativism that cannot be achieved by descriptivist computational-level analysis, illustrating our position with Hypothetical Thinking Theory and the theory of the suppositional conditional. We conclude that descriptivism is a viable option, and that theories of higher mental processing would be better off freed from normative considerations. (shrink)

Algorithmic-level specifications carry part of the explanatory burden in most psychological theories. It is, thus, inappropriate to limit a comparison and evaluation of theories to the computational level. A rational analysis considers people's goal-directed and environmentally adaptive rationality; it is not normative. Adaptive rationality is by definition non-absolute; hence, neither deductive logic nor Bayesian probability theory has absolute normative status.

Although a focus on individual differences can help resolve issues concerning performance errors and computational complexity, the understanding/acceptance axiom is inadequate for establishing which decision norms are most appropriate. The contribution of experience to automatic and controlled processes suggests difficulties in attributing interactional intelligence to goals of evolutionary rationality and analytic intelligence to goals of instrumental rationality.

Relevant to philosophy, law, management, and artificial intelligence, these papers explore the applicability of nonmonotonic or defeasible logic to normative reasoning. The resulting systems purport to solve well-known deontic paradoxes and to provide a better treatment than classical deontic logic does of prima facie obligation, conditional obligation, and priorities of normative principles.

Paradoxical individual differences, where a dysfunctional trait correlates positively with some preconceived notion of the normatively correct answer, provide compelling evidence that the wrong norm has been adopted. We have found that logical performance on conditional inference is positively correlated with schizotypy. Following Stanovich & West's reasoning, we conclude that logic is not normative in conditional inference, the prototypically logical task.

Elqayam & Evans (E&E) argue against prescriptive normativism and in favor of descriptivism. I challenge the assumption, implicit in their article, that there is a choice to be made between the two approaches. While descriptivism may be the right approach for some questions, others call for a normativist approach. To illustrate the point, I briefly discuss two questions of the latter sort.