Self-Referential Justifications in Epistemic Logic

This paper is devoted to the study of self-referential proofs and/or justifications, i.e.,valid proofs that prove statements about these same proofs. The goal is to investigate whether such self-referential justifications are present in the reasoning described by standard modal epistemic logics such as $\mathsf{S4}$ . We argue that the modal language by itself is too coarse to capture this concept of self-referentiality and that the language of justification logic can serve as an adequate refinement. We consider well-known modal logics of knowledge/belief and show, using explicit justifications, that $\mathsf{S4}$ , $\mathsf{D4}$ , $\mathsf{K4}$ , and $\mathsf{T}$ with their respective justification counterparts $\mathsf{LP}$ , $\mathsf{JD4}$ , $\mathsf{J4}$ , and $\mathsf{JT}$ describe knowledge that is self-referential in some strong sense. We also demonstrate that self-referentiality can be avoided for $\mathsf{K}$ and $\mathsf{D}$ . In order to prove the former result, we develop a machinery of minimal evidence functions used to effectively build models for justification logics. We observe that the calculus used to construct the minimal functions axiomatizes the reflected fragments of justification logics. We also discuss difficulties that result from an introduction of negative introspectio

Explicit Evidence Systems with Common Knowledge

Justification logics are epistemic logics that explicitly include justifications for the agents' knowledge. We develop a multi-agent justification logic with evidence terms for individual agents as well as for common knowledge. We define a Kripke-style semantics that is similar to Fitting's semantics for the Logic of Proofs LP. We show the soundness, completeness, and finite model property of our multi-agent justification logic with respect to this Kripke-style semantics. We demonstrate that our logic is a conservative extension of Yavorskaya's minimal bimodal explicit evidence logic, which is a two-agent version of LP. We discuss the relationship of our logic to the multi-agent modal logic S4 with common knowledge. Finally, we give a brief analysis of the coordinated attack problem in the newly developed language of our logic

(WP 2012-01) Samuels on Methodological Pluralism in Economics

Warren Samuels was an influential proponent of methodological pluralism in economics. This short paper discusses his understanding of methodological pluralism, and argues that it is based on three distinct components: (1) his critique of the idea that theories have epistemic foundations and his \u27matrix approach to meaningfulness,\u27 (2) his belief that the absence of meta-principles for science combined with our human psychology create an existential dilemma for theorists and policy-makers, and (3) his understanding of relativism, social constructivism, and \u27limited but affirmative\u27 defense of nihilism against the charge of skepticism. The paper closes with a brief discussion of what Samuels\u27 methodological pluralism might tell us about historiography and the history of economics

Tracing the Territory. A Unitary Foundationalist Account

The paper offers an integrative interpretation of the different lines of thought Wittgenstein was inspecting in On Certainty and what he might have been looking for through them. It suggests that we may have been focusing our attention too strongly in the wrong place and comes to a new conclusion about where the real import of these reflections lies. This leads to an answer to the initially posed question of Foundationalism that revises the way in which there can be said to be a grounding intention in On Certainty

Complexity Issues in Justification Logic

Justification Logic is an emerging field that studies provability, knowledge, and belief via explicit proofs or justifications that are part of the language. There exist many justification logics closely related to modal epistemic logics of knowledge and belief. Instead of modality □ in pure justification logics, or in addition to modality □ in hybrid logics, which has an existential epistemic reading \u27there exists a proof of F,\u27 all justification logics use constructs t:F, where a justification term t represents a blueprint of a Hilbert-style proof of F. The first justification logic, LP, introduced by Sergei Artemov, was shown to be a justification counterpart of modal logic S4 and serves as a missing link between S4 and Peano arithmetic, thereby solving a long-standing problem of provability semantics for S4 and Int. The machinery of explicit justifications can be used to analyze well-known epistemic paradoxes, e.g. Gettier\u27s examples of justified true belief that can hardly be considered knowledge, and to find new approaches to the concept of common knowledge. Yet another possible application is the Logical Omniscience Problem, which reflects an undesirable property of knowledge as described by modality when an agent knows all the logical consequences of his/her knowledge. The language of justification logic opens new ways to tackle this problem. This thesis focuses on quantitative analysis of justification logics. We explore their decidability and complexity of Validity Problem for them. A closer analysis of the realization phenomenon in general and of one procedure in particular enables us to deduce interesting corollaries about self-referentiality for several modal logics. A framework for proving decidability of various justification logics is developed by generalizing the Finite Model Property. Limitations of the method are demonstrated through an example of an undecidable justification logic. We study reflected fragments of justification logics and provide them with an axiomatization and a decision procedure whose complexity (the upper bound) turns out to be uniform for all justification logics, both pure and hybrid. For many justification logics, we also present lower and upper complexity bounds

The Role of Ideas in the Emergence of Convergent Higher Education Policies in Europe: The Case of France. CES Working Paper, no. 73

How do ideas influence public policy ? French higher education is a good case in point. It seems reasonable to think that the recent evolution French universities underwent resulted from the diffusion of the convergent discourse held by most European countries on the need for increased university autonomy and more self regulation. But no empirical evidence proves that this diffusion process occured in the French case. Nevertheless, if the recent contractual policy in France can not be understood as the product of the emergence of new beliefs, of a new vision of the (European higher education) world, it certainly gave rise to the development of a new or paradigm. This leads us to revisit the relation of ideas and public policy in two ways. First in arguing that the causal link between them is not as unidirectional as generally stated. Second that change does not always happen through a paradigmatic revolution, but rather through an incremental process