Defining Conditional Relevance Using Linked Arguments and Argumentation Schemes: a Commentary on Professor Callen's Article, Rationality and Relevancy: Conditional Relevancy and Constrained Resources

In this brief commentary on Professor Callen's article, I would like to offer a defmition of the logical structure ofthe notion of conditional relevance using two components of argument diagramming technology from argumentation theory. This definition will show how conditional relevance is not only important as a key notion in evidence law, but also represents a structure or pattern that is common and fundamentally important in argumentation theory for the study of relevance in logic generally. I will give some reasons to support this definition as a hypothesis, and will show how it offers a precise and useful analysis of conditional relevance. The proposed definition can best be introduced and explained by considering the remarks of Morganl that were instrumental in the wording of Federal Rule of Evidence I04(b),2 usinga particularcasehe citedas an illustration. What Professor Morgan's remarks on Gila Valley, Globe, & Northern Railway v. HalP strongly suggest, as quoted by Callen,4 is that conditional relevance fits a certain pattern of argumentation, as represented in Figure 1 below. To quote Professor Morgan, "[t]o say that the relevancy of A depends upon the existence of B is only to say that it requires a combination of A and B to produce a relevant factor in the case. "S This remark strongly suggests the pattern of what is called a linked argument in argumentation theory. In a linked argument,both premises (in the simplest case of an argument with only two premises) are required to support the conclusion. This contrasts with a