A Sequent Formulation of Conditional Logic Based on Belief Change Operations

Peter Gärdenfors has developed a semantics for conditional logic, based on the operations of expansion and revision applied to states of information. The account amounts to a formalisation of the Ramsey test for conditionals. A conditional A > B is declared accepted in a state of information K if B is accepted in the state of information which is the result of revising K with respect to A. While Gärdenfors's account takes the truth-functional part of the logic as given, the present paper proposes a semantics entirely based on epistemic states and operations on these states. The semantics is accompanied by a syntactic treatment of conditional logic which is formally similar to Gentzen's sequent formulation of natural deduction rules. Three of David Lewis's systems of conditional logic are represented. The formulations are attractive by virtue of their transparency and simplicity.     

Shedding Dialectical Tiers: A Social-Epistemic View

Is there a duty to respond to objections in order to present a good argument? Ralph Johnson argues that there is such a duty, which he refers to as the “dialectical tier“ of an argument. I deny the (alleged) duty primarily on grounds that it would exert too great a demand on arguers, harming argumentation practices. The valuable aim of responding to objections, which Johnson 's dialectical tier is meant to satisfy, can be achieved in better ways, as argumentation is a social-epistemic activity.     

On the Theoretical Unification and Nature of Fallacies

I argue in a non-reductive sense for a plausible epistemic principle, which can (1) theoretically and instrumentally unify or systematize all fallacies, and (2) provide a justification for using such a principle for characterizing an erroneous argument as a fallacy. This plausible epistemic principle involves the idea of an error in the method of justification, which results in a failure to provide relevant evidence to satisfy certain standards of adequate proof. Thus, all fallacies are systematically disguised failures to provide substantive proof: a failure in the attempt to persuade rationally, as opposed to emotionally or rhetorically. I argue that the epistemic idea of begging the question is essential to this idea of a fallacy as an inadequate proof.     

Comments on Plantinga’s Argument of Transworld Identity

Plantinga’s conception of possible worlds is problematic in one sense: it relies on the prior idea of modality. His strategy for resolving the puzzle of transworld identity is significant in the metaphysical sense but fruitless in the epistemological sense because world-indexed properties cannot be used as effectively in epistemic practice as their counterparts, i.e., space- and time-indexed properties. His isolation of transworld identification from transworld identity is unconvincing. This paper argues that the intelligibility of modal discourse and reference is the essence of transworld identity. It is also proved that transworld identification is the epistemic ground of such intelligibility. Hence, the transworld identification problem is the epistemological foundation of the transworld identity problem, and there must be a comprehensive answer to the former.     

Iterated Belief Change and the Recovery Axiom

The axiom of recovery, while capturing a central intuition regarding belief change, has been the source of much controversy. We argue briefly against putative counterexamples to the axiom—while agreeing that some of their insight deserves to be preserved—and present additional recovery-like axioms in a framework that uses epistemic states, which encode preferences, as the object of revisions. This makes iterated revision possible and renders explicit the connection between iterated belief change and the axiom of recovery. We provide a representation theorem that connects the semantic conditions we impose on iterated revision and our additional syntactical properties. We show interesting similarities between our framework and that of Darwiche–Pearl (Artificial Intelligence 89:1–29 1997). In particular, we show that intuitions underlying the controversial (C2) postulate are captured by the recovery axiom and our recovery-like postulates (the latter can be seen as weakenings of (C2)). We present postulates for contraction, in the same spirit as the Darwiche–Pearl postulates for revision, and provide a theorem that connects our syntactic postulates with a set of semantic conditions. Lastly, we show a connection between the contraction postulates and a generalisation of the recovery axiom. Portions of this paper were originally presented at ECAI 2002.     

RELIABILISM AND SAFETY

Abstract: Duncan Pritchard has recently highlighted the problem of veritic epistemic luck and claimed that a safety‐based account of knowledge succeeds in eliminating veritic luck where virtue‐based accounts and process reliabilism fail. He then claims that if one accepts a safety‐based account, there is no longer a motivation for retaining a commitment to reliabilism. In this article, I delineate several distinct safety principles, and I argue that those that eliminate veritic luck do so only if at least implicitly committed to reliabilism.     

A strategy for assessing closure

This paper looks at an argument strategy for assessing the epistemic closure principle. This is the principle that says knowledge is closed under known entailment; or (roughly) if S knows p and S knows that p entails q, then S knows that q. The strategy in question looks to the individual conditions on knowledge to see if they are closed. According to one conjecture, if all the individual conditions are closed, then so too is knowledge. I give a deductive argument for this conjecture. According to a second conjecture, if one (or more) condition is not closed, then neither is knowledge. I give an inductive argument for this conjecture. In sum, I defend the strategy by defending the claim that knowledge is closed if, and only if, all the conditions on knowledge are closed. After making my case, I look at what this means for the debate over whether knowledge is closed.     

Strategic Maneuvering: A Synthetic Recapitulation

As an introduction to the special issue on Perspectives on Strategic Maneuvering, this article provides a synthetic recapitulation of the various steps that were taken in developing the pragma-dialectical theory of strategic maneuvering. First, the concept of strategic maneuvering is described as a means to reconcile the simultaneous pursuit of dialectical and rhetorical aims. Second, strategic maneuvering is related to the various kinds of argumentative activity types in which it takes place. Third, the concept of dialectical profiles is discussed and the parameters that are pertinent to distinguishing between different types of strategic maneuvering. Fourth, the fallacies are viewed as derailment of strategic maneuvering. Fifth, as a case in point, strategic maneuvering with inconsistency is examined. This contribution brings together insights that earlier were put forward in a number of separate publications.     

PHILOSOPHERS OF INTELLECTUAL DISABILITY: A TAXONOMY

Abstract: This essay explores various roles that philosophers occupy in relation to intellectual disability. In examining how philosophers define their object of inquiry as experts and gatekeepers, it raises critical questions concerning the nature of philosophical discourse about intellectual disability. It then goes on to consider three alternate positions, the advocate or friend, the animal, and the "intellectually disabled," each of which points to new ways of philosophizing in the face of intellectual disability.     

Another Paradox In Naive Set-Theory

Reasonning in naive set theory (with unlimited comprehension), we derive a paradox (a formal contradiction) which can be seen as a variant of the Burali-Forti paradox. Presented by Robert Goldblatt