Reasoning from Paradigms and Negative Evidence

Abstract

Reasoning from negative evidence takes place where an expected outcome is tested for, and not found, and then a conclusion is drawn about the significance of the failure to find. By using Gricean maxims and implicatures, we show how a set of alternatives, which we call a paradigm, provides the deep inferential structure on which reasoning from lack of evidence is based. We show that the strength of reasoning from negative evidence depends on how the arguer defines his conclusion and what he considers to be in the paradigm of negated alternatives. If we negate only two of the several possible alternatives, even if they are the most probable, the conclusion will be weak. However, if we deny all possible alternatives, the reasoning will be strong, and even in some cases deductively valid.

Keywords: argument from ignorance, lack of evidence, argumentation, negation, classification under lack of knowledge, defeasible reasoning, burden of proof, Gricean maxims, scalar predicates