  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.
