First-Order Conditional Logic Revisited

Conditional logics play an important role in recent attempts to investigate default reasoning. This paper investigates firstorder conditional logic. We show that, as for first-order probabilistic logic, it is important not to confound statistical conditionals over the domain (such as "most birds fly"), and subjective conditionals over possible worlds (such as "I believe that Tweety is unlikely to fly"). We then address the issue of ascribing semantics to first-order conditional logic. As in the propositional case, there are many possible semantics. To study the problem in a coherent way, we use plausibility structures. These provide us with a general framework in which many of the standard approaches can be embedded. We show that while these standard approaches are all the same at the propositional level, they are significantly different in the context of a first-order language. We show that plausibilities provide the most natural extension of conditional logic to ...

• Type: Conference
• Year: 1996
• Where: AAAI
• Authors: Nir Friedman, Joseph Y. Halpern, Daphne Koller
• Keywords: AAAI 1996, Conditional Logic, First-order Conditional Logic, Firstorder Conditional Logic, Intelligent Agents