Argumentation Schemes for Presumptive Reasoning

Recent concerns with the evaluation of argumentation in informal logic and speech communication center around nondemonstrative arguments that lead to tentative or defeasible conclusions based on a balance of considerations. Such arguments do not appear to have structures of the kind traditionally identified with deductive and inductive reasoning, but are extremely common and are often called "plausible" or "presumptive," meaning that they are only provisionally acceptable even when they are correct. How is one to judge, by some clearly defined standard, whether such arguments are correct or not in a given instance? The answer lies in what are called argumentation schemes -- forms of argument (structures of…