Journal of Information, Law and Technology


Argue!: A Graphical Approach to Legal Argument Mediation



Download 0.86 Mb.
Page5/13
Date26.10.2016
Size0.86 Mb.
1   2   3   4   5   6   7   8   9   ...   13

4. Argue!: A Graphical Approach to Legal Argument Mediation


The graphical approach is demonstrated by the Argue!-system. Its underlying argumentation theory is based on CumulA, a procedural model of argumentation with arguments and counterarguments [Verheij, 1996]. After introducing CumulA, again a sample session based on the 'bussluis' case is used to illustrate the opportunities of the graphical approach for education. Verheij [1998a] gives a more technically oriented description of the Argue!-system.

4.1 Introducing CumulA


CumulA [Verheij, 1996] is a procedural model of argumentation with arguments and counterarguments. It is based on two main assumptions. The first assumption is that argumentation is a process during which arguments are constructed and counterarguments are adduced. The second assumption is that the arguments used in argumentation are defeasible, in the sense that whether they justify their conclusion depends on the counterarguments available at a stage of the argumentation process.

The goal of argumentation is to (rationally) justify conclusions. In CumulA, the focus is on the process of argumentation, and on the defeasibility of the arguments used in argumentation. Argumentation is a process, in the sense that during argumentation arguments are constructed and counterarguments are brought up. Arguments are assumed to be defeasible, in the sense that if an argument at some stage of the argumentation process justifies its conclusion, it not necessarily justifies its conclusion at all later stages. The defeat of an argument is caused by a counterargument that is itself undefeated.

For instance, if the Municipality has committed a tort against the cab-driver, a conclusion would be that the Municipality has the duty to repair 100% of the damages. The conclusion can be rationally justified, by giving support for it. E.g., the following argument could be given:

The Municipality has committed a tort against the cab-driver.

So, the Municipality has the (general) duty to repair the damages.

So, the Municipality has the duty to repair 100% of the damages.

Recall that in Dutch tort law, the general duty to repair damages and the portion of the damages to be repaired are established consecutively (see section 2.1).

An argument as above is a reconstruction of how a conclusion can be supported. The argument given here consists of two steps.

An argument that supports its conclusion does not always justify it. For instance, if in our example it turns out that the damages are fully imputed to the cab-driver (as in the 'bussluis' case), the conclusion that the Municipality has the duty to repair 100% of the damages would no longer be justified. The argument has become defeated. In the example, the argument

The Municipality has the (general) duty to repair the damages.

So, the Municipality has the duty to repair 100% of the damages.

does not justify its conclusion because of the counterargument

The damages are fully imputed to the cab-driver.

CumulA is a procedural model of argumentation with arguments and counterarguments, in which the defeat status of an argument, either undefeated or defeated, depends on:



  • the structure of the argument;

  • the counterarguments;

  • the argumentation stage.

We briefly discuss each below. The model builds on the work of Pollock [1987, 1995], Loui [1991, 1992], Vreeswijk [1993, 1997] and Dung [1995] in philosophy, artificial intelligence, and was developed to complement the work on Reason-Based Logic (see, e.g., Hage [1993, 1996, 1997] and Verheij [1996]).

In the model, the structure of an argument is represented as in the argumentation theory of Van Eemeren and Grootendorst [1981, 1987]. Both the subordination and the co-ordination of arguments are possible. It is explored how the structure of arguments can lead to their defeat. For instance, the intuitions that it is easier to defeat an argument if it contains a longer chain of defeasible steps ('sequential weakening'), and that it is harder to defeat an argument if it contains more reasons to support its conclusion ('parallel strengthening'), are investigated.

In the model, which arguments are counterarguments for other arguments is taken as a primitive notion [cf. Dung, 1995]. So-called defeaters indicate when arguments can defeat other arguments. It turns out that defeaters can be used to represent a wide range of types of defeat, as proposed in the literature, e.g., Pollock's [1987] undercutting and rebutting defeat. Moreover some new types of defeat can be distinguished, namely defeat by sequential weakening (related to the well-known sorites paradox) and defeat by parallel strengthening (related to the accrual of reasons).

In the model, argumentation stages represent the arguments and the counterarguments currently taken into account, and the status of these arguments, either defeated or undefeated. The model’s lines of argumentation, i.e., sequences of stages, give insight in the influence that the process of taking arguments into account has on the status of arguments. For instance, by means of argumentation diagrams, which give an overview of possible lines of argumentation, phenomena that are characteristic for argumentation with defeasible arguments, such as the reinstatement of arguments, are explicitly depicted. In contrast with Vreeswijk's [1993, 1997] model, we show how in a line of argumentation not only new conclusions are inferred, but also new reasons are adduced.

To summarise, CumulA shows


  1. how the subordination and co-ordination of arguments is related to their defeat;

  2. how the defeat of arguments can be described in terms of their structure, counterarguments, and the stage of the argumentation process;

  3. how both forward and backward argumentation can be formalised in one model.





Share with your friends:
1   2   3   4   5   6   7   8   9   ...   13


The database is protected by copyright ©sckool.org 2019
send message

    Main page