From Analysis to Evaluation

Abstract

We address some questions concerning argument structure motivated by evaluative considerations. First, what is the relation between the warrants licencing moves from the individual reasons of a convergent argument to the warrant licencing the move from all the stated reasons to the conclusion? How are the strengths of the individual reasons related to the strength of the argument as a whole? The convergent argument has one warrant licencing the move from the conjunction of the premises to the conclusion. The weight of the argument is not a function of the weights of the individual reasons but of the backing of the overall warrant. By contrast, should we have multiple arguments for the same conclusion, the strength of support is the maximum of the strengths of these arguments. Second, should an argument present one or more reasons for a conclusion and acknowledge one or more rebutting defeaters leaving them uncountered–typical of pro versus con arguments–the strength of the argument from the positive reasons is determined by the reliability of the warrant from the conjunction of these reasons and the uncountered defeaters. Finally, we conclude by discussing problems with using Pollock’s inference graphs to determine whether we are justified in accepting a conclusion or whether that justification is defeated. Our reflections indicate that although Pollock wanted to be able to read off the defeat status of conclusions from argument diagrams, evaluating whether believing a conclusion is justified goes beyond graphs or diagrams.