KNOWLEDGE AND ACTION IN RATIONAL DELIBERATION

Douglas WaltonCRRAR

7th Conference on Analytic Philosophy in China, Shanghai, Oct. 30, 2011

Bounded Procedural Rationality

• In this paper it is shown how knowledge can lead to a rational decision for action or inaction based on argumentation process called deliberation.

• The viewpoint adopted is one of bounded procedural rationality based on a notion of defeasible knowledge.

• The problem confronted is that decision-making about real-world problems needs to be made under conditions of uncertainty, and even apparent inconsistency where there is both pro and contra evidence for a conclusion to be decided.

Argumentation Methods

• It is just in this kind of case that methods of argumentation are especially useful.

• Argumentation can be defined as a procedure to identify, analyze and evaluate the arguments on both sides of a claim, and to use the evidence that is collected by this procedure to determine whether to accept the claim or not.

• It is also a part of argumentation methodology that setting a burden of proof on each side by determining what kind of arguments are relevant, and what standards of proof should be required, is an essential requirements of the procedure.

First Example

• Let’s consider the case of the student who is writing an essay. He is collecting all kinds of knowledge from books and periodicals, but he has a strict deadline for finishing the assignment.

• This problem is to determine when he should stop searching for new knowledge and attempt to write the essay. The longer he delays writing in order to search for new knowledge, the better the essay will be. But if he delays too long, he will not have enough time to properly write the essay, and the result will be that the essay will not be very good.

• The general problem in many comparable cases of this kind is one of when to terminate the process of deliberation and close off the collecting of new knowledge.

Second Example• Another kind of example can also be cited. In July 2010, scientists found a way

of altering the DNA of mosquitoes that shortens their lifespan so that malarial parasites to not have enough time to grow to maturity. This discovery gives the scientists the possibility of releasing a malaria-proof mosquito into the wild, thereby eliminating mosquitoes that can cause malaria. Right now malaria kills about one million people every year.

• However, there is a problem. Altering the DNA of mosquitoes might make them better carriers of other diseases.

• This proposal cannot be carried out for another ten years, and even then, there may be no way to know what the consequences are.

• Once the malaria-proof mosquito is produced by the scientists, even though we can study the problem and collect knowledge about it, we will never know what all the side-effects will be until we release the new mosquitoes into the wild.

• R. M. Schneidermann, ‘God lives in a Lab in Arizona’, Newsweek, August 9, 2010, 8.

Aquinas Poses the Problem• Aquinas asked the question, “May deliberation go on endlessly?” and answered

it in his Summa Theologiae in Question 14, Article 6; quoted from (Blackfriars Edition, 155):

• • 1. Yes, apparently, for it is about the particular things which are the concern of

practical knowledge. These are infinite. Accordingly no term is to be set to the inquiry of deliberation about them.

• 2. Further, we have to weigh up not only what has to be done, but also how to clear away the obstacles. Now any number of objections to any particular course of action can be put up and knocked down in our mind. Therefore there is no stop to our questioning about how to deal with them.

• 3. Moreover, the inquiry instituted by demonstrative science does not lead back indefinitely, but arrives at self-evident principles which are altogether certain. Such certainty, however, cannot be found in contingent and individual facts, which are variable and uncertain. Deliberation, therefore, goes on endlessly.

The Closed World Assumption• The closed world assumption is the inference drawn that any positive

fact not specified in a given database may be assumed to be false, on the basis that all of the relevant knowledge has been specified (Reiter, 1987).

• Consider the familiar example (Reiter 1980, 69) of scanning an airline monitor. Let’s say that no direct flight is listed from Windsor to Shanghai. The closed world assumption is that all the relevant data on flights leaving from Windsor at this time are listed on the monitor on the airport website.

• So if a direct Windsor to Shanghai flight is not listed, it is reasonable to draw the conclusion that no such flight is available. In this situation, the closed world assumption is reasonable to invoke, because we have good reason to assume that the knowledge base is complete.

Another Example

• The official listing of baseball statistics about hits, home runs and so forth, is known to not only be complete for the major-league baseball teams, but also highly reliable, because there are many fans who are passionate about keeping baseball statistics, and who would immediately challenge any error they might find in the baseball statistics knowledge base.

• So if we were to look in the database and see that some information about some home runs alleged to be hit in 1936 was not in it, we could very confidently invoke the closed world assumption to draw the conclusion that there were no such home runs hit that year.

Scheme for Practical Reasoning

• Major Premise: I have a goal G.• Minor Premise: Carrying out action A is a means to

realize G.• Conclusion: I ought (practically speaking) to carry out

action A.• The first-person singular pronoun ‘I’ in the scheme for

practical reasoning above represents an agent. An agent is an entity that has goals and knowledge about its circumstances, can take action in its circumstances based on this knowledge, and can also see the consequences of its actions so that it can correct them through feedback.

Critical Questions Matching Scheme

• CQ1: What other goals do I have that should be considered that might conflict with G?

• CQ2: What alternative actions to my bringing about A that would also bring about G should be considered?

• CQ3: Among bringing about A and these alternative actions, which is arguably the most efficient?

• CQ4: What grounds are there for arguing that it is practically possible for me to bring about A?

• CQ5: What consequences of my bringing about A should also be taken into account?

How to Use Critical Questions

• These five basic critical questions for practical reasoning are not complete.

• As shown in (Walton 1990), each of these five critical questions has critical sub-questions.

• The five basic critical questions are meant as devices to help a critic or student of critical thinking find weak points in an argument of this type that can be challenged or cast into doubt.

Value-based Practical Reasoning• Value-based practical reasoning (Atkinson, Bench-Capon and

McBurney, 2006) is made up of two more basic schemes, the one for practical reasoning and the one for argument from values (Bench-Capon, 2003). The argumentation scheme for value-based practical reasoning has this form (Atkinson, Bench-Capon and McBurney, 2006).

• • Scheme for Value-based Practical Reasoning• • In the current circumstances R• we should perform action A• to achieve New Circumstances S• which will realize some goal G• which will promote some value V.

Questioning versus Arguing

• Asking the critical question C5 needs to be backed up with some evidence of what the negative consequences are before an argument based on practical reasoning is refuted.

• When this happens, the asking of this critical question can also be analyzed as a counter-argument.

• Argument from negative consequences cites the consequences of a proposed course of action as a reason against taking that course of action.

• This argument also has a positive form in which positive consequences of an action are cited as a reason for carrying out the action.

Argument from Consequences• Scheme for Argument from Positive Consequences• • Major Premise: Its having good consequences is a reason for doing

something.• Minor Premise: If A is brought about, good consequences will plausibly occur.• Conclusion: A should be brought about.• • Scheme for Argument from Negative Consequences• • Major Premise: Its having good consequences is a reason for not doing

something.• Minor Premise: If A is brought about, then bad consequences will occur.• Conclusion: A should not be brought about.

The Carneades System

• The Carneades Argumentation System uses argumentation schemes and critical questions for argument analysis and evaluation (Gordon, 2010).

• Carneades is a computational model consisting of mathematical structures and functions on them (Gordon, Prakken and Walton, 2007).

• Carneades models the structure of arguments, the acceptability of statements, and burdens of proof.

• Carneades has an open source graphical user interface (http://carneades.github.com/ ).

Tweety Example

Wiki Example 1

Problem with Critical Questions

• It would be very nice if the five critical questions for practical reasoning could be represented as additional premises of the argumentation scheme. Then we could represent the critical questions as implicit assumptions of the argument when we analyze the argument using an argument diagram of the standard kind.

• However, there is a problem. With some critical questions, simply asking the question is enough to defeat the original argument, whereas with other critical questions, merely asking the critical question is not enough to defeat the argument. In order to defeat the argument some evidence has to be given to back up the critical question.

Solution to the Problem

• To solve this problem, the Carneades system offers two ways of responding the asking of a critical question by distinguishing three types of premises in argumentation scheme, called ordinary premises, assumptions and exceptions (Walton and Gordon, 2009).

• Ordinary premises are explicitly stated premises of the argumentation scheme. They are assumed to hold tentatively, but if challenged they may have to be given up.

• Assumptions, like ordinary premises, are assumed to be true. • Exceptions are assumed not to hold, and therefore they do not

defeat an argument unless backed up by evidence to support them.

Carneades Map of Practical Reasoning

Evaluating Arguments• Based on this method of representing the critical questions of an

argumentation scheme by representing them as different kinds of premises of scheme, Carneades has a computational method for evaluating arguments (Gordon and Walton, 2006).

• At each stage of the argumentation process, an effective method (decision procedure) is used for testing whether the conclusion of an argument is acceptable or not, given knowledge about whether its premises are acceptable or not.

• The assumptions represent undisputed facts, the current consensus of the participants, or the commitments or beliefs of some agent, depending on the task.

• The evaluation of the given argument may depend on the proof standard applicable to the proposition at issue, and on the dialogue procedure the argument is embedded in.

Dialogue Models

• Dialogue models have rules on how participants should ideally speak and respond in order to achieve a common conversational goal.

• Dialogue models of argumentation (Walton and Krabbe, 1995) have proved their usefulness in argumentation studies, artificial intelligence, and multi-agent systems (Bench-Capon, 2003; Prakken, 2005).

• Walton and Krabbe (1995) identified six primary types of dialogue: information-seeking dialogue, inquiry, deliberation, persuasion dialogue, negotiation and eristic (quarrelsome) dialogue.

Formal Dialogue Systems

• A dialogue is generally a group activity with multiple participants, but in the simplest case there are only two parties called the proponent and the respondent.

• A dialogue is defined in the Carneades model as an ordered 3-tuple <O, A, C> where O is the opening stage, A is the argumentation stage, and C is the closing stage (Gordon and Walton, 2009, 5).

• Dialogue protocols regulate the types of moves that are allowed and how a participant must respond to a previous move made by the other party (Walton and Krabbe, 1995).

• So far, Carneades has not provided protocols for deliberation dialogues, but there is a formal model.

Deliberation Dialogue• The initial situation of deliberation is the need for action arising out of a

choice between alternative competing courses of action. • The collective goal of this type of dialogue is for the participants to

collectively decide on what is the best available proposal for action that has been put forward for the group at the proposal stage, once that stage has been reached.

• Once that stage has been reached, the participants evaluate the proposals in a process in which each party puts forward its own proposals and critically evaluates the competing proposals put forward by others.

• There is also a prior ‘inform’ stage where the facts collected and shared among the participants.

• In a successful deliberation, the strengths and weaknesses of each proposal are brought out by the discussion, and this evidence is used to judge which proposal is the one that should be selected to move forward with.

8 Stages of Deliberation Dialogue• Open: In this stage a governing question is raised about what is to be done. A

governing question, like ‘Where shall we go for dinner this evening?’ is posed.• Inform: This stage includes discussion of desirable goals, values, constraints on

possible actions, evaluation criteria for proposals, and determination of relevant facts.

• Propose: Proposals cite possible action-options relevant to the governing question• Consider: This stage concerns commenting on the proposals from various

perspectives.• Revise: Goals, constraints, perspectives, and action-options are revised in light of

comments presented and information gathering as well as fact-checking.• Recommend: A proposal for action is recommended for acceptance or non-

acceptance by each participant.• Confirm: The participants can confirm acceptance of the recommended proposal

according to some procedure they have agreed on.• Close: The termination of the dialogue takes place.• (Hitchcock, McBurney and Parsons, 2007)

Judging a Deliberation Dialogue

Scientific Inquiry and Truth• According to the traditional view the conclusion of an inquiry has

to be drawn by the deductive chain of reasoning from a set of premises that are absolutely certain.

• Any scientific inquiry might lead to a conclusion which might need to be revised in the future (Peirce, 1931, 2.75). Popper called this falsifiability.

• Peirce wrote that many things are “substantially certain” (Peirce 1931, 1.152), but that this is different from the kind of absolute certainty that implies truth.

• On his view truth is an important motivation for scientists to have as the ultimate goal of scientific research, but he argued that that truth can only be arrived at beyond all doubt by an inquiry that would take an infinite amount of time.

Fallibilism of Peirce and Popper

• On their view, knowledge does not imply truth. In other words, it is not a requirement for proposition to be part of knowledge that it be true, at least in any sense requiring that it will not turn out to be false in the future.

• On this view, called fallibilism, scientific knowledge is defeasible, meaning that even though a proposition is accepted as knowledge, it might be defeated in the future by enough evidence casting doubt on it, or even showing that it is false, so that it needs to be retracted.

Defeasible Knowledge• Peirce described the process of inquiry as one in which different

participants set out with conflicting views, but are led through a process of marshalling and testing evidence to accepting the same conclusion. This convergence takes place as a successful inquiry moves to completion.

• According to (Walton, 2010) Peircean belief is characterized as a settled state we do not wish to change. Once fixed, it is something we cling tenaciously to. It is an indication of a habit, and a matter of degree.

• It puts us into a condition so we act in a certain way in the future, and it guides our desires and shapes our actions.

• On this view, defeasible knowledge is a species of belief that is fixed firmly by a scientific discipline through process of inquiry that tests the belief as a hypothesis against all the pro and contra evidence that can be collected and is relevant to proving or disproving it.

Proof Standards• The following four standards of proof are used in the Carneades

Argumentation System (Gordon and Walton, 2009).• Scintilla of Evidence (SE) is met if there is at least one applicable argument

for a claim. • Preponderance of the Evidence (PE) is met if SE is satisfied and the maximum

weight assigned to an applicable pro argument (for the claim) is greater than the maximum weight of an applicable con argument (against the claim).

• Clear and Convincing Evidence (CCE), is met if PE is satisfied, the maximum weight of applicable pro arguments exceeds some threshold α, and the difference between the maximum weight of the applicable pro arguments and the maximum weight of the applicable con arguments exceeds some threshold β.

• Beyond Reasonable Doubt (BRD) is met if CCE is satisfied and the maximum weight of the applicable con arguments is less than some threshold γ.

The Mosquitoes Example

• The collection of knowledge phase will only be reached at some point after ten years. At this point there will have to be deliberations that many organizations will take part in, including the World Health Organization, which will need to develop rules for testing genetically modified mosquitoes.

• However, even at this point, it is possible to see how the argumentation structure of the deliberation in this case takes a pro and contra argument form based on argumentation schemes.

Carneades Map of Mosquitoes Argumentation

Evaluation of Mosquitoes Case• This method of moving forward with an evaluating deliberation

requires taking fully into account evidence obtained from scientific inquiry into the circumstances of the case.

• On this model, the factual basis of evidence from the scientific inquiry is part of what is required to assess the depth of assessment of the proposals made in the deliberation dialogue.

• The dialogue should only be closed when this depth of assessment by argumentation has met the standard of evidence set for this deliberation dialogue.

• At some point the cost in lives due to malaria will require that the decision be made one way or the other, provided that the alternative of doing nothing continues to result in highly significant loss of human lives.

Conclusion

• The paper has shown how a rational decision on what to do depends on an evaluation of the pro and contra arguments for each proposal, once all the proposals have been stated.

• It has also shown that this decision depends on how well informed these proposals are, based on the scientific and factual evidence concerning the circumstances of the case.

• To provide a method for making these decisions, the paper has utilized formal dialectical models of deliberation dialogue and inquiry dialogue, showing how the latter type of dialogue is embedded in the former.

3 Problems for Further Research

• The first is to devise computational argumentation tools to measure the depth of argumentation behind a proposal that has been discussed in a deliberation dialogue by the closing stage.

• The second is to show how knowledge is transferred from inquiry dialogue to deliberation dialogue, typically using the argumentation scheme for argument from expert opinion.

• The third is to apply the methods of this paper to a more detailed example of deliberation using knowledge obtained from scientific inquiry.

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