A Sufficient Condition for Gaining Belief in Byzantine Fault-Tolerant Distributed Systems

Existing protocols for byzantine fault tolerant distributed systems usually rely on the correct agents' ability to detect faulty agents and/or to detect the occurrence of some event or action on some correct agent. In this paper, we provide sufficient conditions that allow an agent to infer the appropriate beliefs from its history, and a procedure that allows these conditions to be checked in finite time. Our results thus provide essential stepping stones for developing efficient protocols and proving them correct.Comment: In Proceedings TARK 2023, arXiv:2307.0400

The Role of A Priori Belief in the Design and Analysis of Fault-Tolerant Distributed Systems

The debate around the notions of a priori knowledge and a posteriori knowledge has proven crucial for the development of many fields in philosophy, such as metaphysics, epistemology, metametaphysics etc. We advocate that the recent debate on the two notions is also fruitful for man-made distributed computing systems and for the epistemic analysis thereof. Following a recently proposed modal and fallibilistic account of a priori knowledge, we elaborate the corresponding concept of a priori belief: We propose a rich taxonomy of types of a priori beliefs and their role for the different agents that participate in the system engineering process, which match the existing view exceedingly well and are particularly promising for explaining and dealing with unexpected behaviors in fault-tolerant distributed systems. Developing such a philosophical foundation will provide a sound basis for eventually implementing our ideas in a suitable epistemic reasoning and analysis framework and, hence, constitutes a mandatory first step for developing methods and tools to cope with the various challenges that emerge in such systems

Logics of knowledge and action: critical analysis and challenges

International audienceWe overview the most prominent logics of knowledge and action that were proposed and studied in the multiagent systems literature. We classify them according to these two dimensions, knowledge and action, and moreover introduce a distinction between individual knowledge and group knowledge, and between a nonstrategic an a strategic interpretation of action operators. For each of the logics in our classification we highlight problematic properties. They indicate weaknesses in the design of these logics and call into question their suitability to represent knowledge and reason about it. This leads to a list of research challenges

Causality, Knowledge and Coordination in Distributed Systems

Effecting coordination across remote sites in a distributed system is an essential part of distributed computing, and also an inherent challenge. In 1978, an analysis of communication in asynchronous systems was suggested by Leslie Lamport. Lamport's analysis determines a notion of temporal precedence, a sort of weak notion of time, which is otherwise missing in asynchronous systems. This notion has been extensively utilized in various applications. Yet the analysis is limited to systems that are asynchronous. In this thesis we go beyond by investigating causality in synchronous systems. In such systems, the boundaries of causal influence are not charted out exclusively by message passing. Here time itself, passing at a uniform (or almost uniform) rate for all processes, is also a medium by which causal influence may fan out. This thesis studies, and characterizes, the combinations of time and message passing that govern causal influence in synchronous systems. It turns out that knowledge based analysis [FHMV] provides a well tailored formal framework within which causal notions can be studied. As we show, the formal notion of knowledge is highly appropriate for characterizing causal influence in terms of information flow, broadening the analysis of Chandy and Misra in [ChM]. We define several generic classes of coordination problems that pose various temporal ordering requirements on the participating processes. These coordination problems provide natural generalizations of real life requirements. We then analyze the causal conditions that underlie suitable solutions to these problems. The analysis is conducted in two stages: first, the temporal ordering requirements are reduced to epistemic conditions. Then, these epistemic conditions are characterized in terms of the causal communication patterns that are necessary and sufficient to bring them about.Comment: PhD Dissertatio

Toward an Analysis of the Abductive Moral Argument for God’s Existence: Assessing the Evidential Quality of Moral Phenomena and the Evidential Virtuosity of Christian Theological Models

The moral argument for God’s existence is perhaps the oldest and most salient of the arguments from natural theology. In contemporary literature, there has been a focus on the abductive version of the moral argument. Although the mode of reasoning, abduction, has been articulated, there has not been a robust articulation of the individual components of the argument. Such an articulation would include the data quality of moral phenomena, the theoretical virtuosity of theological models that explain the moral phenomena, and how both contribute to the likelihood of moral arguments. The goal of this paper is to provide such an articulation. Our method is to catalog the phenomena, sort them by their location on the emergent hierarchy of sciences, then describe how the ecumenical Christian theological model exemplifies evidential virtues in explaining them. Our results show that moral arguments are neither of the highest or lowest quality yet can be assented to on a principled level of investigation, especially given existential considerations

When to Trust Authoritative Testimony: Generation and Transmission of Knowledge in Saadya Gaon, Al-Ghazālī and Thomas Aquinas

People have become suspicious of authority, including epistemic authorities, i.e., knowledge experts, even on matters individuals are unqualified to adjudicate (e.g., climate change, vaccines, or the shape and age of the earth). This is problematic since most of our knowledge comes from trusting a speaker—whether scholars reading experts, students listening to teachers, children obeying their parents, or pedestrians inquiring of strangers—such that the knowledge transmitted is rarely personally verified. Despite the recent development of social epistemology and theories of testimony, this is not a new problem. Ancient and Medieval philosophers largely took it for granted that most human knowledge primarily comes from listening to a trustworthy speaker whose virtuous character serves to mitigate against the twin concerns of inaccuracy and dishonesty. Thus, unlike contemporary Social Epistemology, few testimonial theories were explicitly laid out despite the crucial role testimony plays throughout a wide range of topics and teachings. To date, the working theory of testimony underpinning the works of medieval philosophers are just now being codified. This is particularly relevant for the Abrahamic faiths since they originate with testimony from God himself. The goal of this dissertation is to explore how the generation and transmission of religious knowledge (i.e., testimonial theory) appears in an exemplary thinker from each faith: Saadya (Sa\u27adiah) Gaon of Judaism (882-942), al-Ghazālī of Islam (1058-1111), and Thomas Aquinas of Christianity (1225-1274). While not contemporaries, these exemplars are theological philosophers who are like-minded in their desire to maintain an orthodox faith while possessing philosophical approaches to truth. Thus, they maintained sophisticated epistemological theories of generation and transmission within their own religious contexts (e.g., revelation, scripture, and prophecy). Cataloguing these medieval testimonial theories reveals a historical incongruity with the current contemporary concept of testimony and its frameworks. Based on the testimonial theories of these three thinkers, I argue for a transhistorical concept of testimony that does not presume an evidentialist framework to account for pre-modern theories of testimony which predominantly rely on virtue theoretic frameworks. To test the proposed neutral framework, I offer a virtue epistemological account of testimony in which trust is not an intellectual virtue, but the intellectual aspect of the historic virtue of autonomy. I argue that intellectual autonomy and trust are inversely related in one\u27s interactions with authority (both practical and theoretical)