In Chapter 2 we examined some relatively simple (but real) cases in which argument diagramming tools, along with argumentation schemes and critical questions, were used to identify and analyze practical reasoning. Now we need to go more deeply into the subject to address the question of how the kind of practical reasoning we have identified can be formally modeled. There are some existing formal models in artificial intelligence that can model this kind of practical reasoning, in addition to the value-based system introduced in Chapter 1. Some of these formal models have been implemented in computational systems that contain argument diagramming tools. In Chapter 3, the reader will be introduced to these formal models and computational tools, in order to show how they can be used to model practical reasoning.

The way Araucaria is applied to the various examples of arguments in health ads in Chapter 2 was very instructive because it showed how the scheme for practical reasoning, along with other arguments – some of them also based on known schemes – can be structured in a way that makes the sequence of reasoning in a case easy to interpret and analyze. A nice feature of Araucaria was that once the scheme is identified as fitting a particular segment of the chain of argumentation represented in the argument diagram, the menu can be displayed showing the critical questions matching the scheme. This particular device turned out to be extremely helpful because, as indicated in Chapter 1, the main tool needed for evaluating instances of argumentation containing practical reasoning is the list of critical questions matching a scheme.

Argument diagramming, even along with argumentation schemes, is not sufficient to yield a model of the structure of practical reasoning as a species of rational argumentation. For that purpose, we need a precise formal model that goes more deeply into the structure of practical reasoning. In this chapter, it will be shown how some existing formal argumentation systems can be applied to practical reasoning. It will also prove helpful if the formal model is implemented in a working computational system that has additional features useful for analyzing practical reasoning, including an argument diagramming interface.