Conclusion
JAMs do not offer a complete self-contained analysis of knowledge but rather reduce knowledge to knowledge-producing justifications accepted by the agent. This, however, constitutes meaningful progress because it decomposes knowledge in a way that moves justification objects to the forefront of epistemic modeling.
Note that the Gettier and Russell examples clearly indicate which justifications are knowledge-producing or accepted. So JAMs fairly model situations in which the corresponding properties of justifications (knowledgeproducing, accepted) are given.There are many natural open questions that indicate possible research directions. Are justification assertions checkable, or decidable for an agent? Is the property of a justification to be knowledge-producing checkable by the agent? In multiagent cases, how much do agents know about each other and about the model? Do agents know each other's accepted and knowledge-producing justifications? What is the complexity of these new justification logics and what are their feasible fragments that make sense for epistemic modeling?