Bryan Renne

Public communication in justification logic

Justification Logic is a framework for reasoning about evidence and justification in multi-agent systems. Most accounts of Justification Logic are essentially static, in that the (justified) beliefs of agents are immutable. In this article, we add public communication, a dynamic operation of belief change studied in the area of Dynamic Epistemic Logic, to the language of Justification Logic. Introducing notions of bisimulation for the languages of Justification Logic with and without public communication, we catalogue the expressive relationships that exist between almost all of the well-known static fragments of Justification Logic and then determine whether the addition of public communication affects the various expressive relationships existing between these fragments.

The Logic of Justified Belief Change, Soft Evidence and Defeasible Knowledge

We present a logic for reasoning about the evidence-based knowledge and beliefs and the evidential dynamics of non-logically -omniscient agents. We do this by adapting key tools and techniques from Dynamic Epistemic Logic, Justification Logic, and Belief Revision so as to provide a lightweight, yet fine-grained approach that characterizes well-known epistemic and doxastic attitudes in terms of the evidential reasoning that justifies these attitudes. We then add the dynamic operations of evidence introduction, evidence-based inference, strong acceptance of new evidence (evidential “upgrade”), and irrevocable acceptance of additional evidence (evidential “update”). We exemplify our theory by providing a formal dynamic account of Lehrer’s well-known Gettier-type scenario involving the famous Ferrari and the infamous Messrs. Nogot and Havit.

The logic of justified belief, explicit knowledge, and conclusive evidence

We present a complete, decidable logic for reasoning about a notion of completely trustworthy (“conclusive”) evidence and its relations to justifiable (implicit) belief and knowledge, as well as to their explicit justifications. This logic makes use of a number of evidence-related notions such as availability, admissibility, and “goodness” of a piece of evidence, and is based on an innovative modification of the Fitting semantics for Artemovʼs Justification Logic designed to preempt Gettier-type counterexamples. We combine this with ideas from belief revision and awareness logics to provide an account for explicitly justified (defeasible) knowledge based on conclusive evidence that addresses the problem of (logical) omniscience.

Multi-agent Justification Logic: communication and evidence elimination

This paper presents a logic combining Dynamic Epistemic Logic, a framework for reasoning about multi-agent communication, with a new multi-agent version of Justification Logic, a framework for reasoning about evidence and justification. This novel combination incorporates a new kind of multi-agent evidence elimination that cleanly meshes with the multi-agent communications from Dynamic Epistemic Logic, resulting in a system for reasoning about multi-agent communication and evidence elimination for groups of interacting rational agents.

Evidence elimination in multi-agent justification logic

This paper presents a logic combining Dynamic Epistemic Logic, a framework for reasoning about multi-agent communication, with a new multi-agent version of Justification Logic, a framework for reasoning about evidence and justification. This novel combination incorporates a new kind of multi-agent evidence elimination that cleanly meshes with the multi-agent communications from Dynamic Epistemic Logic, resulting in a system for reasoning about multi-agent communication and evidence elimination for groups of interacting rational agents.

Logics of temporal-epistemic actions

We present Dynamic Epistemic Temporal Logic, a framework for reasoning about operations on multi-agent Kripke models that contain a designated temporal relation. These operations are natural extensions of the well-known “action models” from Dynamic Epistemic Logic (DEL). Our “temporal action models” may be used to define a number of informational actions that can modify the “objective” temporal structure of a model along with the agents’ basic and higher-order knowledge and beliefs about this structure, including their beliefs about the time. In essence, this approach provides one way to extend the domain of action model-style operations from atemporal Kripke models to temporal Kripke models in a manner that allows actions to control the flow of time. We present a number of examples to illustrate the subtleties involved in interpreting the effects of our extended action models on temporal Kripke models. We also study preservation of important epistemic-temporal properties of temporal Kripke models under temporal action model-induced operations, provide complete axiomatizations for two theories of temporal action models, and connect our approach with previous work on time in DEL.

Simple Evidence Elimination in Justification Logic

Suppose that the prosecutor presents the jury with exhibit x 1, an audio recording of a boss ordering his subordinate to falsify the accounting ledgers so as to deceive the investors into thinking that his insolvent company is not actually insolvent. Suppose further that the judge provides the jury with oral instructions x 2 stating that the jury may use the following principle in reaching its verdict: “if the boss ordered his subordinate to falsify the ledgers, then the boss is guilty of fraud.” Using the principle described by the judge’s instructions x 2, the recording x 1 provides the jury with sufficient evidence to find the boss guilty of fraud.