Using Schemes for Argument Detection in Legal Texts

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Using Schemes for Argument Detection in Legal
Texts

• ICAIL 2009, Friday June 12
• NaLELA Workshop
• Douglas Walton (CRRAR)
• University of Windsor

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Five Tasks for Research

• The first task is the identification of arguments
  in a text of discourse, as opposed to other
  entities, like statements, questions or
  explanations. Carrying out this task requires
  some working definition of what an argument is,
  as opposed to say an explanation.
• The second task is the identification of
  argumentation schemes. The principal way of
  recognizing a particular argumentation scheme is
  to be able to identify the premises and the
  conclusion that make up that scheme by
  recognizing terms like expert.
• The third task is the classification of
  argumentation schemes. For example, argument from
  expert opinion is a subspecies of the scheme for
  argument from position to know.
• The fourth task is the precise formulation of
  schemes. One part of it is to formulate schemes
  used in particular fields. For example, the
  scheme for argument from expert opinion may have
  to be formulated in a more precise way in law.
• The fifth task is to develop criteria to enable
  the differentiation between schemes that are
  similar to each other. To develop techniques for
  minimizing errors, a corpus of borderline problem
  cases of this sort can be used to develop
  criteria for separation.

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Argument from Position to Know 309

• Major Premise Source a is in position to know
  about things in a certain subject domain S
  containing proposition A.
• Minor Premise a asserts that A is true (false).
• Conclusion A is true (false).
• Critical Questions
• CQ1 Is a in position to know whether A is true
  (false)?
• CQ2Is a an honest (trustworthy, reliable)
  source?
• CQ3Did a assert that A is true (false)?

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Argument from Expert Opinion

• Major Premise Source E is an expert in subject
  domain S containing proposition A.
• Minor Premise E asserts that proposition A is
  true (false)
• Conclusion A is true (false)
• Critical Questions
• CQ1 How credible is E as an expert source?
• CQ2 Is E an expert in the field that A is in?
• CQ3 What did E assert that implies A?
• CQ4 Is E personally reliable as a source?
• CQ5 Is A consistent with what other experts
  assert?
• CQ6 Is E's assertion based on evidence?

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A Classification System

• The automated classification of schemes is aided
  by a proposed classification system given by
  Walton, Reed and Macagno (2008, 349-350).
• There are three main categories.
• Reasoning, like practical reasoning, abductive
  reasoning, deductive reasoning etc..
• Source-Based Arguments, like argument from
  position to know, argument from testimony.
• Applying Rules to Cases, like analogy, precedent,
  arguing from a rule to a case.
• Then the various schemes are placed under each
  main category.

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Classification 1 of Schemes
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Classification 2 of Schemes
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More Subtle Schemes

• Some schemes are hidden because they are so
  simple and commonly used every day that we are
  most often unaware we are using them.
• Argument from ignorance (aka lack of evidence
  reasoning).
• Argument from commitment.

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Enthymemes

• All men are mortal, therefore Socrates is mortal.
• Implicit premise that Socrates is a man.
• In this instance, the missing premise is based on
  common knowledge.
• Inference to the best explanation.

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Enthymemes and Schemes

• Example Markley lives in California and tells me
  the weather is beautiful there.
• The scheme for argument from position to know can
  be used to help interpret the text as the
  following argument.
• The weather is good in California since Markley
  has asserted this and is in a position to know
  about this.
• The scheme can be used to help identify missing
  premises.

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Use of Contextual Clues

• In some cases, it may be hard to identify a
  scheme, but clues from the context of dialog can
  help. Consider the following example.
• The Blood Pressure Dialog Example (Restificar,
  Ali and McRoy, 1999, 3)
• Proponent Have you had your blood pressure
  checked?
• Respondent There is no need.
• Proponent Uncontrolled high blood pressure can
  lead to heart attack, heart failure, stroke or
  kidney failure.

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Using Critical Questions

• The interesting thing about this example is that
  we may not know the argumentation scheme fitting
  the argument put forward by the proponent, but we
  do know the scheme fitting the rebuttal put
  forward by the proponent after the respondent
  replies.
• The rebuttal clearly fits the scheme for argument
  from negative consequences.
• This observation offers a clue as to how to
  identify the scheme, since argumentation from
  negative consequences (side effects) is commonly
  used to critically question practical reasoning.

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Scheme for Practical Inference (WRM, 2008, 323)

• Major Premise I have a goal G.
• Minor Premise Carrying out this action A is a
  means to realize G.
• Conclusion Therefore, I ought to carry out this
  action A.
• Critical Questions
• CQ1 What other goals might conflict with G?
• CQ2 What alternative actions should be
  considered?
• CQ3 Among these alternative actions, which is
  the most efficient?
• CQ4 Is it is practically possible for me to
  bring about A?
• CQ5 What consequences of my bringing about A
  should also be taken into account?

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Argument from Waste (WRM, 2008, 326)

• Premise 1 If a stops trying to realize A now,
  all as previous efforts torealize A will be
  wasted.
• Premise 2 If all a's previous attempts to
  realize A are wasted, that would be a bad thing.
• Conclusion Therefore, a ought to continue trying
  to realize A.

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Is it Argument from Waste?

• The Stem Cell ExampleThis position is
  shortsighted and stubborn. The fact is, fetuses
  are being aborted whether conservatives like it
  or not. Post-abortion, the embryos are literally
  being thrown away when they could be used in
  life-saving medical research. It has become a
  matter of religious and personal beliefs, and
  misguided ones at that. Lives could be saved and
  vastly improved if only scientists were allowed
  to use embryos that are otherwise being tossed in
  the garbage.

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Whats Missing?

• What appears to be missing is that in a proper
  argument from waste, as required by premise 1 of
  the scheme, the agent was making some previous
  efforts to do something, and if he stops now, his
  efforts will be wasted.
• In the stem cell example, there were no previous
  efforts of this sort. Instead, what is said to be
  a waste are the embryos that are thrown away.
• Premise 2 of the scheme for argument from waste
  also requires that if previous attempts to
  realize something are wasted, that would be a bad
  thing. There seems to be nothing fitting this
  premise in the stem cells example. Nobody was
  doing anything with the stem cells previously. No
  effort or commitment was being put into doing
  something with them.

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The Problem of Enthymemes

• Would it be possible to build an automated system
  that could detect enthymemes and fill in the
  missing premises or conclusions so that an
  analysis of the argument with its missing
  premises indicated could be provided by an
  argument visualization tool?
• The short answer is that it might be a lot more
  difficult to build such a useful tool of this
  kind than one might initially think (Walton and
  Reed, 2005), but the use of schemes would be
  helpful as part of the tool.

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Gordon and Walton (ICAIL 09)

• Argument reconstruction can be viewed as an
  application of abductive reasoning, using the
  scheme for abductive reasoning.
• This scheme and others are used as patterns to
  construct a set of alternative interpretations of
  the text.
• These interpretations form the set of hypotheses
  for abductive reasoning.
• The task is then to choose the interpretation
  among the hypotheses which best explains the text
  and other contextual evidence.

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Abductive Scheme WRM, 329

• Argumentation Scheme for Abductive Reasoning
• Premise 1 D is a set of data or supposed facts
  in a case.
• Premise 2 Each one of a set of accounts is
  successful in explaining D.
• Premise 3 E is the account that explains D most
  successfully
• Conclusion E is the most plausible hypothesis in
  the case.
• Critical questions
• CQ1 How satisfactory is E itself as an
  explanation of D, apart from the alternative
  explanations available so far in the dialogue?
• CQ2 How much better an explanation is E than the
  alternative explanations offered so far in the
  dialog?
• CQ3 How far has the dialog progressed? If the
  dialogue is an inquiry, how thorough has the
  search been in the case?
• CQ4 Would it be better to continue the dialog
  further, instead of drawing a conclusion at this
  point?

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Problems to be Solved

• What is an explanation as a kind of communicative
  action?
• How is offering an explanation different from
  offering an argument?
• It is a problem that often discourse indicators
  are insufficient (hard to tell).
• The answer is to be sought in the purpose of the
  communicative act.

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References

• Raquel Mochales-Palau and Marie-Francine Moens,
  Study on Sentence Relations in the Automatic
  Detection of Argumentation in Legal Cases, Legal
  Knowledge and Information Systems JURIX 2007,
  The Twentieth International Conference, ed. Arno
  R. Lodder and Laurens Mommers, Amsterdam IOS
  Press, 2007, 89-98
• Iyad Rahwan, Bita Banihashemi, Chris Reed and
  Douglas Walton, Avicenna Argumentation Support
  on the Semantic Web, to appear.
• Angelo Restificar, Syed S. Ali and Susan W.
  McRoy, ARGUER Using Argument Schemas for
  Argument Detection and Rebuttal in Dialogs,
  UMP99 International Conference on User Modeling,
  ed. Judy Kay, New York, Springer-Wien, 315-317.
• Frans H. van Eemeren, Peter Houtlosser and
  Francsica Snoek Henkemans, Argumentative
  Indicators in Discourse, Dordrecht, Springer,
  2007.
• Douglas Walton, The Sunk Costs Fallacy or
  Argument from Waste, Argumentation, 16, 2002,
  473-503. 
• Douglas Walton and Chris Reed, Argumentation
  Schemes and Enthymemes, Synthese An
  International Journal for Epistemology,
  Methodology and Philosophy of Science, 145, 2005,
  339-370.
• Douglas Walton, Chris Reed and Fabrizio Macagno,
  Argumentation Schemes, Cambridge, Cambridge
  University Press, 2008.