Artificial argument assistants for defeasible argumentation

Bart Verheij

Presented by: Jacob Halvorson

Goal: Develop experimental argument assistance systems

• Reasons– Administering and supervising the argument process

– Keeping track of:• Issues raised

• Assumptions made

• Reasons for and against a conclusion

– Evaluating the justification status of the statements

– Checking for user error regarding rules of argument

Who would this help?

• Single user:– Lawyer could use it in court

• Analyze current arguments

• Structure unpolished arguments

• More than one user:– Argument mediation system

• Keep track of diverging positions

• Assist in the evaluation of opinions

Isn’t this like an Automated Reasoning System?

• Automated Reasoning– Knowledge base– Complex reasoning is done for user

• Argument Assistant– Assist user in reasoning (not replace user’s

reasoning)• Complexities are less problematic since reasoning

can be left to user

Argument Assistant and the Legal System

• This paper focuses on using argument assistants to help with legal proceedings

• Difficulties– Lack of a canonical theory of defeasible

argumentation– New user interface must be designed

• How to present arguments to the user• How users may perform argument moves

– Legal• Legal rules are generally defeasible• Legal gap• Legal ambiguity

Dialectical Theory Construction

Theory of the case, applicable law and the consequences are progressively developed

ARGUE!• Argument assistant based on the logical

system CUMULA– CUMULA: Arguments (trees of reasons and

conclusions) can be defeated• Defeat of arguments results from attack by other

arguments (defeaters).• Types of defeat

– Undefeated counterargument– Undefeated argument with conflicting conclusion

• Problems– Not natural enough to represent real-life

argumentation– On-screen drawing too complex

ARGUMED 2.0• Major problems fixed from ARGUE!

– Argumentation theory focused undercutting exceptions

• Reasons that block the connection between a reason and a conclusion

• Support by reasons and undercutting exceptions could be represented simultaneously.

– User interface is template-based• Buttons to click which will bring up a given

template

• Evaluated by ten testers– Show unexplained examples and try to

reproduce argumentation samples in the system• ARGUMED based on DEFLOG

ARGUMED based on DEFLOG

• Mouse-sensitive argument screen– Add a statement box by double-clicking– Right mouse gives access to

• Add support for statement• Attack against statement

• Better argumentation theory– May attack any statement – Arrows between a reason and its (supported or

attacked) conclusion are considered conditional statements

ARGUE! and ARGUMED based on DEFLOG in a case of

inflicting grievous bodily harm• Precedent 1

– Victim has several broken ribs, but no complications

• Precedent 2– Victim has several broken ribs with

complications

*Intentional infliction of grievous bodily harm is punishable by 8 years in prison.

ARGUE! evaluation rules

1. A statement that is now set to justified or unjustified by the user, keeps its status.

2. A statement that now has justified support, is next justified.

3. A statement that now has no justified support and is attacked, is next unjustified.

4. A statement that now has no justified support and is not attacked, is next not evaluated.

ARGUE! resultsUser can arrange statements at will White box = justifiedGray box = not justifiedDotted line & Dot = connection no longer justified

User can set status of statement• Justified• Unjustified• Not evaluated

ARGUE! Results (cont’d)

Crossed out box = conclusion unjustifiedLimitations

• Undercutting defeater can’t be challenged• If a statement is a reason for another can’t be

challenged• Ex. Witness is unreliable

ARGUMED based on DEFLOG examples

• Allows support and attack of any statement

ARGUMED based on DEFLOG evaluation rules

1. A statement is justified if and only ifa) It is an assumption, against which there is no defeating reason,

or

b) It is an issue, for which there is a justifying reason.

2. A statement is defeated if and only if there is a defeating reason against it.

3. A reason is justifying if an only if the reason and the conditional underlying the corresponding supporting argument step are justified.

4. A reason is defeating if and only if the reason and the conditional underlying the corresponding attacking argument step are justified.

ARGUMED based on DEFLOG results

• ! = assumptions• ? = issue• Dark bold = justified• Line through text = defeated• Light italic = unevaluated

Result is not justified since inflicting grievous bodily harm is not justified and even defeated by testimony

ARGUMED based on DEFLOG resultsAdding testimonies of 10 pub visitors

• By adding the testimonies of 10 pub visitors, the “grievous bodily harm” statement results in “unevaluated”

ARGUMED based on DEFLOG resultsAttacking a statement

• Adding the rule that several broken ribs with complications count as grievous bodily harm results in the accuser doing the crime

ARGUMED based on DEFLOG screenshot

Conclusion• ARGUE!

– Developed first– Based on CUMULA which isn’t sufficiently

natural to apply to real-life argumentation• Can’t attack any statement

– User interface isn’t intuitive

• ARGUMED based on DEFLOG– Can attack any statement– User interface allows for use of mouse to edit

argumentative data on the screen