Types and Properties
of Dialogue
Lecture of Douglas Walton at University
of Lugano, December 19, 2007
Argument in Dialogue
An argument is a social and verbal
means of trying to resolve, or at least
contend with, a conflict or difference
that has arisen between two parties
engaged in a dialogue (Walton 1990,
p. 411). According to this definition,
an argument necessarily involves a
claim that is advanced by one of the
parties, typically an opinion that the
one party has put forward as true,
and that the other party questions, or
is opposed to.
Reasoning, Argument and Explanation
Reasoning can be used for differing purposes, for
example in explanations and arguments. Reasoning is a
process of inference in passing from certain
propositions known or assumed to be true to other
propositions in a sequence(Walton, 1990). Abductive
reasoning is inference to the best explanation (Walton,
2004). Practical reasoning seeks out a prudential line of
conduct for an agent in a particular situation, while
theoretical reasoning seeks evidence that counts for or
against the truth of a proposition (Walton, 1990).
Abductive Reasoning
• I see some tracks on the trail, and they look
like bear tracks.
• This is a national park, where one might
expect there are some bears.
• The best explanation is that a bear passed
this way recently.
• Conclusion: a bear passed this way recently.
Practical Reasoning
• Goal Premise: my goal is to give a lecture on
dialogue theory in Lugano on April 17.
• Means Premise: the means for giving the lecture is
to make up some Power Point Slides by April 11.
• Conclusion: I should make up some Power Point
slides by April 11.
• Practical reasoning seeks out a prudential line of
conduct for an agent in a particular situation.
Theoretical Reasoning
• Premise: Everyone who lives in Lugano
lives near Lago Maggiore.
• Premise: Mario lives in Lugano.
• Conclusion: Mario lives near Lago
Maggiore.
• This example is a deductively valid
argument assuming ‘everyone’ is universal.
What is an Explanation?
The new dialectical theory (Walton, 2005, chapter
6) models an explanation as a dialogue between two
agents in which one agent is presumed by the other
to understand something, and the other agent asks a
question meant to enable him to come to understand
it as well. The model articulates the view of Scriven
(2002, p. 49): “Explanation is literally and logically
the process of filling in gaps in understanding, and
to do this we must start out with some
understanding of something.”
Reasoning, Argument and Explanation
Reasoning can be used for differing purposes, for
example in explanations and arguments. Reasoning is a
process of inference in passing from certain
propositions known or assumed to be true to other
propositions in a sequence. Abductive reasoning
combines explanation with argument. Here we mention
again the distinction between theoretical reasoning and
practical reasoning. Theoretical reasoning provides
evidence that a conclusion is true or false. Practical
reasoning concludes that action should be taken.
How to Tell the Difference
Test to judge whether a given text of discourse contains an
argument or an explanation.
Take the statement that is the thing to be proved or explained,
and ask yourself the following question. Is it taken as an
accepted fact, or something that is in doubt? If the former, it’s
an explanation. If the latter, it’s an argument.
The Goal of Dialogue is Different
The purpose of an argument is to get the hearer to come to
accept something that is doubtful or unsettled. The purpose of
an explanation is to get him to understand something that he
already accepts as a fact.
Speech Act
• SPEECH ACT: "in saying something, we do something",
as when a minister joins two people in marriage saying, "I
now pronounce you husband and wife."
• Examples
• Greeting (in saying, "Hi John!", for instance), apologizing
("Sorry for that!"), asserting something ("It is snowing"),
asking a question ("Is it snowing?"), making a request
("Could you pass the salt.”) or making a promise ("I
promise I'll give it back") are typical examples of speech
acts. In saying, "Watch out, the ground is slippery", Peter
performs the speech act of warning Mary to be careful.
• In saying, "I will try my best to be at home for dinner",
Peter performs the speech act of promising to be at home
in time. [Wikipedia]
Speech Act Moves in a Dialogue
Goal of Dialogue
Sequence of Moves
Turn-taking
Respondent's Move
Speech Act
Post-condition
Proponent's Move
Pre-condition
Initial Situation
Speech Act
Example of a Hamblin Dialogue
Each member in the sequence is defined by Hamblin (1971, p. 130) as a triple, n, p,l . n
represents the length of the dialogue (the number of moves so far). p is a participant.
And l is a what Hamblin calls a locution. Using Hamblin’s notation, a small dialogue
with three moves for far could be represented as follows.
Small Dialogue:
0,P0 ,L4 ,1,P1,L3 ,2,P0,L2 
In the simplest case, there are two participants, called the proponent and the
respondent. When either party makes any move (speech act), the rules determine
which statements are inserted into, or deleted from that participant’s commitment set.
Rules define what kinds of moves can be made and what response move needs to be
made just after the other party’s last move. Rules define when a sequence of dialogue
successfully realizes the communal goal of the dialogue. Each party has a goal, and the
dialogue as a whole has what can be called a communal goal.
Dialogue Typology
Dialogue
Persuasion
Critical Discussion
Information Seeking
Interview
Negotiation
Advice Solicitation
Scientific Inquiry
Expert Consultation
Inquiry
Deliberation
Public Inquiry
Eristic
Quarrel
Properties of Six Basic Types of Dialogue
TYPE OF
DIALOGUE
INITIAL
SITUATION
PARTICIPANT’S
GOAL
GOAL OF DIALOGUE
Persuasion
Conflict of Opinions
Persuade Other
Party
Resolve or Clarify Issue
Inquiry
Need to Have Proof
Find and Verify
Evidence
Prove (Disprove)
Hypothesis
Negotiation
Conflict of Interests
Get What You Most
Want
Reasonable Settlement
that Both Can Live
With
InformationSeeking
Need Information
Acquire or Give
Information
Exchange Information
Deliberation
Dilemma or
Practical Choice
Co-ordinate Goals
and Actions
Decide Best Available
Course of Action
Eristic
Personal Conflict
Verbally Hit Out at
Opponent
Reveal Deeper Basis of
Conflict
Four Systems of Persuasion
Dialogue
Four minimal systems of dialogue were constructed in
(Walton, 1984) as structures to model the kinds of
argumentation used in connection with fallacies. They
start from a minimal one called CB, and proceed to
successively stronger versions.
You can find this book as a pdf file on my web page.
http://io.uwinnipeg.ca/~walton/books/LDG84bk.pdf
The Dialogue System CB
• CB is a simple system of persuasion dialogue in
which two parties, White and Black each have a
thesis to be proved.
• Each tries to prove his/her thesis using only
arguments that have commitments of the other
side as premises.
• A commitment is a statement that a party has gone
on record as accepting by putting forward a
statement, like, “Lugano is north of Milan”.
Locution Rules of CB
•
•
•
•
Statements: Statement letters, S, T, U, ..., are
permissible locutions, and truth-functional
compounds of statement-letters.
Withdrawals: ‘No commitment S’ is the locution
or withdrawal (retraction) of a statement.
Questions: The question ‘S?’ asks ‘Is it the case
that S is true?’
Challenges: The challenge ‘Why S?’ requests
some statement that can serve as a basis in (a
possibly defeasible) proof for S.
Commitment Rules of CB
•
•
•
•
•
After a player makes a statement, S, it is included in his
commitment-store.
After the withdrawal of S, the statement S is deleted from the
speaker's commitment store.
‘Why S?’ places S in the hearer's commitment-store unless it is
already there or unless the hearer immediately retracts his
commitment to S.
Every statement that is shown by the speaker to be an immediate
consequence of statements that are commitments of the hearer then
becomes a commitment of the hearer's and is included in his
commitment store.
No commitment may be withdrawn by the hearer that is shown by
the speaker to be an immediate consequence of statements that are
previous commitments of the hearer.
Dialogue Rules of CB
•
•
•
Each speaker takes his turn to move by
advancing once locution at each turn. A nocommitment locution, however, may accompany
a why-locution as one turn.
A question ‘S?’ must be followed by (i) a
statement ‘S’, (ii) a statement ‘Not-S’, or (iii)
‘No commitment S’).
‘Why S?’ must be followed by (i) ‘No
commitment S’ or (ii) some statement ‘T’, where
S is a consequence of T.
Deliberation Dialogue
• A group of concerned citizens is getting
together to decide whether to support a
proposal for a new sewer system in their
municipality. They have a town hall
meeting.
• Arguments are presented on both sides.
• Example: the new system would be too
costly.
Five Stage Model of Deliberation
Dialogue
Stage 1: Opening the dialogue.
Stage 2: Sharing information.
Stage 3: Making proposals and counter-proposals.
Stage 4: Confirming accepted proposals.
Stage 5: Closing the dialogue.
(McBurney, Hitchcock and Parsons, 2007)
Information-Seeking Dialogue
• Current problem with contradictions in
scientific finding on nutrition and health:
“too much information” (Newsweek,
March 13 cover story, p. 46).
• Information-seeking requires not only
transmission of “facts” (ask-tell), but also
critical analysis of reliability of “facts”.
Classification of Subtypes
Simple InformationSeeking
Interview
Expert Consultation
Examination
(Peirastic)
Educational
Employment
Celebrity
Media
Interview
Interrogation
Examination
(Exestastic)
Witness
Examination
(in Trial)
Four Meanings of ‘Examination’
The first meaning is indicated by the example of examining
something under a microscope. It conveys the idea of looking
at something, some given datum carefully. A second meaning
is the kind of examination typical of testing a student’s
knowledge, for example in a “final examination”. A third is
the examination of a patient by a physician. The physician
looks at the patient’s body, or the parts that are of concern. A
fourth meaning refers to the examination of a witness in a
court. This fourth meaning refers to a kind of dialogue
between a questioner and a respondent. The witness answers
the questions of the examiner, and the answers count as legal
evidence. When the other side gets its turn to question the
witness, the dialogue is called a cross-examination.
Interrogation Dialogue
The goal of an interrogation is to get information from a
party who has it, and who is trying to conceal it, or is likely
to be reluctant to give it out. The interrogation is an attempt
to get some information needed for a specific purpose. It
may be information that is needed for a practical purpose,
for example to save lives, in the case of the interrogation of
a terrorist, or in a military case of prisoner interrogation. Or
it may be police interrogation where the purpose is to get
evidence, for example evidence of the kind needed in a
criminal investigation.. Because of its embedding into a
deliberation, the rules for interrogation dialogue are not
based on agreement, and are not collaborative in the way the
rules for a critical discussion are. Threats and deceptive
moves are legitimate.
Examining an Expert Opinion
When an opinion or argument of an expert
needs to be critically probed or even
attacked, the dialogue is more like a
critical discussion than a purely
information-seeking type of dialogue. The
skill of the questioner in examination
dialogue is to judge what kind of question
is best to ask at a given move in the
sequence of a dialogue. The method for
evaluating argumentation in such
sequences of questions and replies is the
profile of dialogue.
A Small Profile of Dialogue
Proponent
Respondent
Why should I accept A?
Because B
Why should I accept B?
Because C
I do not accept C
If B then C?
Yes, I accept that
Do you accept B?
Yes, I accept that
Then you must accept C
Examples of Dialectical Shifts
• A contractor and homeowner are negotiating on the price
of a foundation repair, and they shift to the issue of
whether it would be a good idea to install and additional
inch of concrete wall.
• During a divorce dispute, the couple are negotiating on
who should looks after the children, but the mediator shifts
the discussion to a persuasion dialogue on the issue of
which party is in the best position to undertake the task of
looking after the children. Each side must give reasons,
and this shift makes the dialogue less eristic.
o f f e r ( P i, O n + 1 )
[s e t v a lu e : i t o r]
[re a s o n s ]
pe rs ua s ion dia logue
[n o re a s o n s ]
Embedding
of Persuasion
into
Negotiation
Dialogue
(Walton and
Godden,
2005)
Pr
[n o s u c c e s s ]
[s u c c e s s ]
re s p o n d s t o o ffe r
[re je c t ]
[a c c e p t ]
s tate o f
[n o re a s o n s ]
ag re e m e n t
[re a s o n s ]
pe rs ua s ion dia logue
[n o s u c c e s s ]
[s u c c e s s ]
P r de c ide s:
R e so lut io n st ill p o ssible ?
[y e s ]
[n o ]
s tate o f
n on -ag r e e m e n t
P r p r o p o se s
c o un t e r - o f f e r
[y e s ]
[n o ]
P r r e que st s
r e v ise d o f f e r
[P i d o e s n o t re v is e o ffe r]
[P i re v is e s o ffe r]
References
Charles L. Hamblin, Fallacies, London, Methuen, 1970.
Charles L. Hamblin, Mathematical Models of Dialogue, Theoria, 7, 1971, 130-155.
James D. Mackenzie, ‘Question Begging in Non-Cumulative Systems’, Journal of
Philosophical Logic, 8, 1979, 117-133.
Peter McBurney, David Hitchcock and Simon Parsons, ‘The Eightfold Way of Deliberation
Dialogue’, International Journal of Intelligent Systems, 22, 2007, 95-132.
Chris Reed and Douglas Walton, Towards a Formal and Implemented Model of Argumentation
Schemes in Agent Communication, Autonomous Agents and Multi-Agent Systems, 11, 2005,
173-188.
Douglas Walton, Logical Dialogue-Games and Fallacies, Lanham, University Press of America,
1984. Available under ‘Books’ on the web page of Douglas Walton:
http://io.uwinnipeg.ca/~walton/
Douglas Walton and David M. Godden, ‘Persuasion Dialogue in Online Dispute Resolution’,
Artificial Intelligence and Law, 13, 2005, 273-295.