Reasoning with Partial Knowledge

We investigate how sociological argumentation di ers from the classical rstorder logic. We focus on theories about age dependence of organizational mortality. The overall pattern of argument does not comply with the classical monotonicity principle: adding premises does not overturn conclusions in an argument. The cause of nonmonotonicity is the need to derive conclusions from partial knowledge. We identify meta-principles that appear to guide the observed sociological argumentation patterns, and we formalize a semantics to represent them. This semantics yields a new kind of logical consequence relation. We demonstrate that this new logic can reproduce the results of informal sociological theorizing and lead to new insights. It allows us to unify existing theory fragments and paves the way towards a complete classical theory. Reasoning with Partial Knowledge Observed inferential patterns which seem `wrong' according to one notion of inference might just as well signal that the speaker is engaged in correct execution of another style of reasoning. (Johan van Benthem [1996])