The way in which knowledge progresses, and especially our scientific knowledge, is by unjustified anticipations, by guesses, by tentative solutions to our problems, by conjectures. These conjectures are controlled by criticism: that is, by attempted refutations, which include severely critical tests. They may survive these tests; but they can never be positively justified: they can neither be established as certainly true nor even as 'probable'. Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us (...) understand the difficulties of the problems which we try to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory - that is, of a tentative solution to our problem - is always a step forward that takes us nearer the truth. And this is how we can learn from our mistakes. As we learn from our mistakes our knowledge grows, even though we may never know - that is, know for certain. Since our knowledge can grow, there can be no reason here for despair of reason. And since we can never know for certain, the can be no authority here for any claim to authority, for conceit over our knowledge, or for smugness. The essays and lectures of which this book is composed apply this thesis to many topics, ranging from problems of the philosophy and history of the physical and social sciences to historical and political problems. (shrink)

Knowledge is a highly valued state in which a person is in cognitive contact with reality. It is, therefore, a relation. On one side of the relation is a conscious subject, and on the other side is a portion of reality to which the knower is directly or indirectly related. While directness is a matter of degree, it is convenient to think of knowledge of things as a direct form of knowledge in comparison to which knowledge about things is indirect. (...) The former has often been called knowledge by acquaintance since the subject is in experiential contact with the portion of reality known, whereas the latter is propositional knowledge since what the subject knows is a true proposition about the world. Knowing Roger is an example of knowledge by acquaintance, while knowing that Roger is a philosopher is an example of propositional knowledge. Knowledge by acquaintance includes not only knowledge of persons and things, but also knowledge of my own mental states. In fact, the knower's own mental states are often thought to be the most directly knowable portion of reality. (shrink)

This article concerns the structure of defeasible arguments like: 'If Bob has red spots, Bob has the measles; Bob has red spots; therefore Bob has the measles.' The issue is whether such arguments have the form of modus ponens or not. Either way there is a problem. If they don't have the form of modus ponens, the common opinion to the contrary taught in leading logic textbooks is wrong. But if they do have the form of modus ponens, doubts are (...) raised about the conventional dogma that all arguments having the form of modus ponens are deductively valid. By carefully examining arguments on both sides of the issue, reasonable doubts are raised about the view that all arguments having a modus ponens form are valid. (shrink)

Harald Thorsrud - Cicero on his Academic Predecessors: the Fallibilism of Arcesilaus and Carneades - Journal of the History of Philosophy 40:1 Journal of the History of Philosophy 40.1 1-18 Cicero on his Academic Predecessors: the Fallibilism of Arcesilaus and Carneades Harald Thorsrud IN AN IMPORTANT PAPER, Couissin argued for what has come to be called the dialectical interpretation of Academic skepticism. On this interpretation, Arcesilaus and Carneades practiced the same, purely dialectical method -- they would elicit assent to premises (...) characteristic of their interlocutor's position and then derive unacceptable consequences exclusively on the basis of those premises. This method allowed them to remain uncommitted to the premises as well as the conclusions of their arguments. They would simply draw logical consequences from their opponents' own premises for the sake of refutation. This is in keeping with the current consensus that an ancient skeptic is one who has no beliefs, or at least no beliefs of a problematically dogmatic sort. Consequently, the methods of ancient skeptics, including Academic skeptics, are thought to be strictly negative, seeking only the elimination of belief. So when we come to Cicero's Philonian version of Academic methodology and find that it explicitly includes provisions for the acquisition of fallible beliefs, it is no surprise that commentators who are sympathetic to the dialectical interpretation tend to view.. (shrink)

We present a mathematical approach to defeasible reasoning based on arguments. This approach integrates the notion of specificity introduced by Poole and the theory of warrant presented by Pollock. The main contribution of this paper is a precise, well-defined system which exhibits correct behavior when applied to the benchmark examples in the literature. It aims for usability rather than novelty. We prove that an order relation can be introduced among equivalence classes of arguments under the equi-specificity relation. We also prove (...) a theorem that ensures the termination of the process of finding the justified facts. Two more lemmas define a reduced search space for checking specificity. In order to implement the theoretical ideas, the language is restricted to Horn clauses for the evidential context. The language used to represent defeasible rules has been restricted in a similar way. The authors intend this work to unify the various existing approaches to argument-based defeasible reasoning. (shrink)

ABSTRACT Inspired by legal reasoning, this paper presents a semantics and proof theory of a system for defeasible argumentation. Arguments are expressed in a logic-programming language with both weak and strong negation, conflicts between arguments are decided with the help of priorities on the rules. An important feature of the system is that these priorities are not fixed, but are themselves defeasibly derived as conclusions within the system. Thus debates on the choice between conflicting arguments can also be modelled. The (...) semantics of the system is given with a fixpoint definition, while its proof theory is stated in dialectical style, where a proof takes the form of a dialogue between a proponent and an opponent of an argument: an argument is shown to be justified if the proponent can make the opponent run out of moves in whatever way the opponent attacks. (shrink)

The essays in this volume represent an approach to human knowledge that has had a profound influence on many recent thinkers. Popper breaks with a traditional commonsense theory of knowledge that can be traced back to Aristotle. A realist and fallibilist, he argues closely and in simple language that scientific knowledge, once stated in human language, is no longer part of ourselves but a separate entity that grows through critical selection.

Isaac Levi uses C. S. Peirce's fallibilism as a foil for his own "epistemological infallibilism". I argue that Levi's criticisms of Peirce do not hit their target, and that the two pragmatists agree on the fundamental issues concerning background knowledge, certainty, revision of belief, and the aims of inquiry.

The article outlines a general epistemological theory of argument: a theory that regards providingjustified belief as the principal aim of argumentation, and defends it instrumentalistically. After introducing some central terms of such a theory, answers to its central questions are proposed: the primary object and structure of the theory, the function of arguments, which is to lead to justified belief, the way such arguments function, which is to guide the addressee's cognizing, objective versus subjective aspects of argumentation, designing different types (...) of argument. Then the notion of ' valid argument' is defined and criteria for the adequate use of such arguments are introduced. Finally, this conception is justified as, among others, leading to more true beliefs than competing conceptions. (shrink)

The article outlines a general epistemological theory of argument: a theory that regards providingjustified belief as the principal aim of argumentation, and defends it instrumentalistically. After introducing some central terms of such a theory (2), answers to its central questions are proposed: the primary object and structure of the theory (3), the function of arguments, which is to lead to justified belief (4), the way such arguments function, which is to guide the addressee's cognizing (5), objective versus subjective aspects of (...) argumentation (6), designing different types of argument (7). Then the notion of '(argumentatively) valid argument' is defined and criteria for the adequate use of such arguments are introduced (8). Finally, this conception is justified as, among others, leading to more true beliefs than competing conceptions (9). (shrink)

This paper studies the modelling of legal reasoning about evidence within general theories of defeasible reasoning and argumentation. In particular, Wigmore's method for charting evidence and its use by modern legal evidence scholars is studied in order to give a formal underpinning in terms of logics for defeasible argumentation. Two notions turn out to be crucial, viz. argumentation schemes and empirical generalisations.

This book identifies 25 argumentation schemes for presumptive reasoning and matches a set of critical questions to each.

Epistemic logic is the branch of philosophical thought that seeks to formalize the discourse about knowledge. Its object is to articulate and clarify the general principles of reasoning about claims to and attributions of knowledge. This comprehensive survey of the topic offers the first systematic account of the subject as it has developed in the journal literature over recent decades. Rescher gives an overview of the discipline by setting out the general principles for reasoning about such matters as propositional knowledge (...) and interrogative knowledge. Aimed at graduate students and specialists, Epistemic Logic elucidates both Rescher's pragmatic view of knowledge and the field in general. (shrink)

A comprehensive introduction to the theory of knowledge.