Logics of Reasonable Information Sources

Extending the work of Belnap [3], we continue our research on ESP structures, consisting of information sources and a processor which collects information from the sources, and develops it further using certain coherent rules. We examine the case of reasonable sources which provide coherent information, characterize the logic of a single reasonable source, and prove that the logics generated by ESP structures with reasonable sources coincide with the general source-processor logics described in our previous work. However, we show that, unlike the case of arbitrary sources, there are processor valuations in general ESP structures which cannot be obtained from any finite number of valuations defined by reasonable sources.