The relation asserts that the context c 2 is more general than the context c 1. Formalizing common-sense reasoning needs contexts as objects, in order to match human ability to consider context explicitly. The proposed database of general common-sense knowledge will make assertions in a general context called C 0. However, C 0 cannot be maximally general, because it will surely involve unstated presuppositions. Indeed we claim that there can be no maximally general context.
Every context involves unstated presuppositions, both linguistic and factual.
Sometimes the reasoning system will have to transcend C 0, and tools will have to be provided to do this. For example, if Boyle's law of the dependence of the volume of a sample of gas on pressure were built into C 0, discovery of its dependence on temperature would have to trigger a process of generalization that might lead to the perfect gas law. The following ideas about how the formalization might proceed are tentative. Moreover, they appeal to recent logical innovations in the formalization of nonmonotonic reasoning. Almost all previous discussion of context has been in connection with natural language, and the present paper relies heavily on examples from natural language.