The Persistence of False Memory: Brain in a Vat Despite Perfect Clocks

TL;DR

This paper extends an epistemic reasoning framework for multi-agent systems to include various system assumptions and demonstrates that perfect synchronization cannot prevent 'brain-in-a-vat' scenarios in such systems.

Contribution

It introduces a modular extension framework for epistemic reasoning in fault-tolerant distributed systems and applies it to analyze fault detection and the limits of synchronization.

Findings

Synchronous and lock-step synchronous agents' fault detection abilities analyzed.

Extended framework encodes reliable, time-bounded, multicast, synchronous, and coordinated actions.

Perfect clocks do not prevent 'brain-in-a-vat' scenarios in synchronized systems.

Abstract

Recently, a detailed epistemic reasoning framework for multi-agent systems with byzantine faulty asynchronous agents and possibly unreliable communication was introduced. We have developed a modular extension framework implemented on top of it, which allows to encode and safely combine additional system assumptions commonly used in the modeling and analysis of fault-tolerant distributed systems, like reliable communication, time-bounded communication, multicasting, synchronous and lock-step synchronous agents and even agents with coordinated actions. We use this extension framework for analyzing basic properties of synchronous and lock-step synchronous agents, such as the agents' local and global fault detection abilities. Moreover, we show that even the perfectly synchronized clocks available in lock-step synchronous systems cannot be used to avoid "brain-in-a-vat" scenarios.