Argumentation and explanation in the context of dialogue
Floris Bex1 and Katarzyna Budzynska2
Abstract. Whilst computational argumentation and computational
explanation have both been studied intensively in AI, models that incorporate both types of reasoning are only just starting to emerge.
The two forms of reasoning need to be clearly distinguished, as they
may influence dialogue protocol and strategy. We show that this distinction can be made by considering the speech acts used to put forth
the reasoning structures. Using the language of the Argument Interchange Format, ideas from speech act theory are integrated into a
conceptual model that allows us to perform both argumentative andexplanatory reasoning.

1

INTRODUCTION

Reasoning can be characterized as the process of moving from certain starting statements, assumptions or premises, to other statements, conclusions [17]. At the same time, reasoning is also the outcome of this process (i.e. the product), a static structure. Reasoning
is typically used in the context of argumentation, where premises areoffered as proof of a conclusion or a claim often in order to persuade
someone or settle an issue. However, reasoning is also used in thecontext of explanation, where the explananda (facts to be explained)
are explained by a coherent set of explanans (facts that explain). The
usual purpose of explanation is not necessarily to convince someone
but rather to help someone understand why the explananda are thecase. In this paper, we aim to explore the similarities and differences
between argumentation and explanation and make a first step towards
an integrated computational model of the two.
Both argumentation and explanation are well-presented in theirrespective sub-fields of AI. A number of computational models ofargumentation have emerged and matured in the past twenty-or-soyears [10] and the computational aspects of the dialectics of argument (cf. [6]) and of the structure of argument [9] are well understood. Computational models for explanation are mainly based on
the technique of abductive (model-based) reasoning, which has beenstudied in the context of medical and system diagnosis (e.g. [3, 8]);other examples of computational explanation are [4], who models
explanatory dialogues, and [14], who uses explanations for natural
language understanding. Despite the important role explanations canplay in argumentative dialogue, there have not been many attempts
to combine argumentation and explanation into one formal model.
Perhaps the most thorough work thus far is [2], who combines structured arguments (cf. [10]) with abductive-causal reasoning into one
model of inference to the best explanation. Other formal work thatmentions both explanation and argumentation is [8].
1 School of Computing, University of Dundee, Dundee, UK, DD1 4HN,

Argumentation and explanation are often used in concert when
performing complex reasoning: explanations can themselves be thesubject of argumentation or they may be used in an argumentative
way. Hence, we need a model that integrates argumentation and explanation. In such a model, the two types of reasoning should beclearly distinguished, because argumentation and explanation havedifferent properties and in a dialogical setting the difference can influence protocol and strategies of dialogue. This distinction is notalways easy to make because of the overlap between argumentationand explanation and the shifting between them in complex dialogue.
It is even more complicated in the case of “reasoning-as-product”,
that is, distinguishing between static arguments and explanations,which often have a similar (logical) structure.
In our opinion, the only way to distinguish between argumentationand explanation is by looking at the context in which the reasoning
was originally performed. In this paper, we concentrate on the contextual property of the intention of the speaker. We are interested in
how to represent the connection between the intentions and the static
reasoning structure under consideration. In this paper, we show that
this connection can be made by using ideas from speech act theory[15]. More specifically, not the propositional contents of a speech act(i.e. that which forms the static reasoning structure) but rather the illocutionary force of the speech act in a dialogue determines whether
reasoning is argumentation or explanation. We will use the conceptual model of the Argument Interchange Format [5, 12] so as to provide a model that is not tied to any specific dialogue or argument
formalism.
The rest of this paper is organized as follows. In section 2 we elaborate on the (structural and contextual) similarities and differences
between argumentation and explanation and we give some intuitive
examples of both types of reasoning. Section 3 discusses our ideas
for a conceptual framework for argumentation and explanation. Finally, section 4 discusses some preliminary conclusions and ideas
for future research.

2

SIMILARITIES AND DIFFERENCES

Argumentation is a type of reasoning used in a specific probative
function, to prove a claim [17]. By its very nature, it involves some
sort of opposition between parties3 and reasons are not just given to
support for a conclusion but also to remove an opponent’s doubts
about this conclusion. For example, a reasoning α ` β is argumentation when β is questioned (dubious) and a proponent of this argument
uses α not only to support β, but also to remove an opponent’s doubts
about β. Explanation, on the other hand, has not as its main goal toprove but rather to explicate why something is the case. Explanation

email: florisbex@computing.dundee.ac.uk
2 Institute of Philosophy, Cardinal Stefan Wyszynski University in Warsaw,

Poland and School of Computing, University of Dundee, Dundee, UK, DD1
4HN, email: k.budzynska@uksw.edu.pl

3

Hence the use of the term ”calculi of opposition” for argumentationtheoretic semantics that allow one to calculate the acceptability of arguments.

in its purest form is not inherently dialectical and an explanation is
given to help the other party, not to convince them. Consider the following example. Say I arrive at work at ten in the morning and myboss asks why I am late. I can either explain to him that the bridge
was open and that I had to wait or I can argue that I am not “late”,
because my contract does not specify the exact hours I have to be at
the office. In first case, I am answering my boss’ question by explaining to him what caused my being late. In the latter case, I am arguing
against my boss claim that I am late.
Argumentation and explanation are often used in conjunction. Explanations can themselves be the subject of argumentation, as one
may argue in support or in opposition of a particular explanation orparts of it. For example, if my boss questions my explanation by arguing that I never cross a bridge on my way to work, I can argue (e.g.
by providing evidence) that I do. Furthermore, explanations may be
used in an argumentative way, as having someone agree to a particular explanation of a phenomenon might help us to persuade them.
For example, if my boss accepts my explanation for being late I might
convince him not to fire me.
Because argumentation and explanation are often intertwined incomplex reasoning, they can sometimes be hard to distinguish fromone another. However, it is important that we do distinguish the two
types of reasoning. Apart from providing a measure of conceptual
neatness, there are also more concrete reasons for not confusing
the two types of reasoning. One of them is that circular arguments
are usually considered fallacious while circular explanations are not.
Take [18]’s recession example. An economist is asked why the economy is in recession in a certain state at present, and she replies:“Right now a lot of people are leaving the state, because taxes are
too high”. But when asked why taxes are so high, she responds:“Well, a lot of people are unemployed, because of the recession”.
The economist has not committed the fallacy of arguing in a circle,
because he was explaining human behavior which has inherent feedback loops. The second reason for correctly distinguishing between
argument and explanation is that the type of reasoning used might
influence the allowed and desired moves in a dialogue. The ways inwhich to correctly respond to an explanation are different from theways in which one should respond to argumentation; for example, itdoes often not make sense for the other party to deny the explananda
whilst it does make sense to deny the conclusion of an argument.
Similarly, a request for information is often better met by explaining
something than by arguing that something is the case.
One possible way of distinguishing between argumentation andexplanation might be to look at the product of reasoning, that is, theargument or the explanation put forth, and the structure and type of
this product. At first sight, it often seems an explanation is abductive
and causal whilst an argument is modus-ponens style, non-causal
reasoning. The basic idea of abductive inference is that if we havea general rule α −→ β, meaning α causes β, and we observe β,
we are allowed to infer α as a possible explanation of β. In contrast,argumentation is often seen as reasoning from a premise α to a conclusion β through an inference rule α −→ β, where this rule need
not necessarily be causal. However, as it turns out it is also possible
to give abductive or causal arguments (see e.g. [19]’s argument fromevidence to hypothesis and causal argument). Similarly, one may perform explanatory reasoning by taking a rule β −→ α, meaning β isevidence for α (see [2] for a discussion on evidential and causal reasoning).
In our opinion, the distinction between argumentation and explanation is not one that is inherent to the product of reasoning, the static
structure. Rather, the distinction follows from the dialogical context

in which the reasoning was originally performed. In order to determine this context, we need not just look at the original intention of
the speaker but also at the broader dialogical context, such as the utterance that was replied to by the speaker and the intentions of theother participants. In other words, the context is largely determinedby the speech acts that were performed (see e.g. [16] for the very
basic concepts of the speech act theory needed in this paper).
According to the pragmatic theory of speech act, argumentationand explanation can be treated as different speech acts. A speech act
Fα, such as: claimα, whyα, consists of an illocutionary force F anda propositional content α. An illocutionary force is an intention ofuttering a propositional content. That is, the performer of a speech
act may utter α with an intention of asserting, asking, promising andso on.
Originally, Searle & Vanderveken recognized argumentation as an
instance of content’s property, i.e. argueα is a speech act consistingof an assertive illocutionary force of uttering α which is a conclusion intended to be supported by premises that the performer of the
speech act provides: “When one argues that P one asserts that P andgives reasons which support the proposition that P , normally withthe perlocutionary intention of convincing the hearer that P ” [16, p.
184]. Observe that in such an account premises of a reasoning are
hidden. For example, the argumentation “I am not late, because mycontract does not specify the exact hours I have to be at the office”
has to be formalized as arguep, where p represents the conclusion “I
am not late”, while the premise “My contract does not specify theexact hours I have to be at the office” remains unexpressed in theformalization.
We use a different approach proposed in [1], where argumentationand explanation are both instances of illocutionary acts that represent a relation between premises and conclusions: argue(α, β) and
explain(α, β), where α denotes a conclusion and β denotes premises.
The distinction between argumentation and explanation cannot justbe made by looking at the original speech act; one also needs to consider the broader dialogical context. In the next section, we show how
this can be represented in the AIF+ .

SPECIFICATION IN THE AIF+

3

In this section, we present how in general the AIF+ describes argument and its context (Section 3.1). Then, we propose how to modelargumentation and explanation in the AIF+ (Section 3.2) and finally
we show how they can be represented as a context of reasoning (Section 3.3).

3.1

Architecture of the AIF+

The AIF+ [13] is a dialogical extensions to the Argument Interchange
Format, AIF (see e.g. [5]). The AIF is an attempt to bring together
a wide variety of argumentation technologies so that they can work
together. The AIF+ extends this approach by allowing to explicitly
handle the context of dialogue in which a reasoning is put forth. It enables to connect the locutions uttered during a dialogue (argument2 )and the underlying arguments expressed by the content of those locutions (argument1 ).
In the AIF+ , the argument1 is represented by two kinds of nodes:• information (I-) nodes, which refer to data, and• scheme (S-) nodes, which refer to the passage between information nodes, which are classified into three groups:– rule application (RA-) nodes which correspond to inference or
support,– conflict application (CA-) nodes which correspond to conflictor refutation,– preference application (PA-) nodes which correspond to value
judgments or preference orderings.

L1 Allen: The Evanston City Council
should make it illegal to tear down thecity’s old warehouses

YA1

I1 The Evanston City
Council should make itillegal to tear down thecity’s old warehouses

TA1
YA2
L2 Beth: What’s the justification forpreserving them?

The argument2 is also described by two types of nodes:• locution nodes (L-), which refer to utterances and constitute a subclass of information nodes, and• transition application (TA-) nodes, which refer to the passage
between locutions and constitute a subclass of rule application
nodes.
The TA-nodes are governed by the protocol of a dialogue system,
recording e.g. that a given assertion has been made in response to an
earlier question. [12] shows two examples of protocols that can be
represented in the AIF+: the Two Party Immediate Response (TPI)[7] and Argument Scheme Dialogue (ASD) [11].
The interaction between argument1 and argument2 is captured bymeans of two types of illocutionary application (YA-) nodes [12]:

TA2

arg
YA3

RA1

L3 Allen: The warehouses are valuable
architecturally

YA4

I2 The warehouses arevaluable architecturally

TA3
L4 Beth: Why are they so valuable?
TA4

expl
YA6

RA2

L5 Allen: The older buildings lend thetown its distinctive character

YA7

I3 The older buildings lend
the town its distinctive
character• the YA-nodes between I-nodes and L-nodes, and• the YA-nodes between RA-nodes and TA-nodes.
For example, an YA-node may represent the relation between an assertion claimα with its propositional content α. The YA-link is determined and warranted (authorized) by the constitutive rules for speechacts [15]. These rules determine what constitutes a successful speechact. For example, an assertion may be unsuccessful and attacked, if
its performer did not have enough evidence for the statement or hedeclared what he actually disbelieves.

3.2

YA-nodesIn this section, we propose the specification of argumentation andexplanation in the AIF+ . We will illustrate it on the example adaptedfrom [18].
Allen The Evanston City Council should make it illegal to tear down
the city’s old warehouses.
Beth What’s the justification for preserving them?
Allen The warehouses are valuable architecturally.
Beth Why are they so valuable?
Allen The older buildings lend the town its distinctive character.
Walton points out that Allen’ first response is argumentation, while
a second one is explanation. We follow this assumption without further considerations.
In the dialogue between Allen and Beth (see Fig. 1), the argument2
consists of five speech acts represented by L-nodes (we use abbreviation Li to denote subsequent locution nodes). The argument1 consistsof three propositions represented by I-nodes (Ii means subsequent
information nodes). The interaction between the argument2 and theargument1 is described by means of the YA-nodes. The speech acts
L1 , L3 and L5 have assertive illocutionary force connecting themwith propositional contents I1 , I2 and I3 , respectively. The passage
between L1 (resp. L3 , L5 ) and I1 (resp. I2 , I3 ) is represented by YA1(resp. YA4 , YA7 ). The illocutionary node YA2 (resp. YA5 ) links the
directive L2 (resp. L4 ) and its propositional content I1 (resp. I2 ): not
all YA-nodes are assertive schemes.
The most interesting is the complex type of illocutionary force
which could be treated as intention of arguing and explaining. In the

YA5

Figure 1. The AIF+ description of the example from [18]AIF+ , the complex illocution is represented by the YA-nodes between RA-nodes and TA-nodes [12]. In Fig. 1, there are two suchnodes: YA3 and YA6 . According to the assumption made above, YA3
corresponds to argumentation and YA6 to explanation. The illocution YA3 links Allen’s response to Beth’s challenge (i.e. TA2 ) withthe argument “The warehouses are valuable architecturally” for theclaim “The Evanston City Council should make it illegal to tear down
the citys old warehouses” (i.e. RA1 ). This captures the intuition that
Allen’s argumentation is invoked by Beth’s challenge. On the other
hand, the illocution YA3 links Allen’s response to Beth’s request for
information (i.e. TA4 ) with the explanation “The older buildings lend
the town its distinctive character” for the claim “The warehouses arevaluable architecturally” (i.e. RA2 ). This captures the intuition that
Allen’s explanation is invoked by Beth’s request for information.
Observe that we could represent argumentation and explanation as
YA4 and YA7 , respectively. However, in such a representation they
are indistinguishable from simple assertion. Assigning argumentation and explanation to the TA- and RA-nodes captures the intuition
that they are social processes that emerge from the interaction between agents such that one agent responds to interlocutor’s request
for justification or explanation.

3.3

Context of reasoning

In Section 2, we emphasized that argumentation and explanation canbe distinguished not by the structural properties of an underlying reasoning, but by its contextual properties. In this section, we propose
how to model argumentation and explanation as a context of reasoning.
In the AIF+ , the context of reasoning structure is represented byargument2 , in which a reasoning was performed, as well as by theinteraction between argument1 and argument2 . The structural indistinguishability of argumentation and explanation means that the samestructure may be either argumentation or explanation depending on
the intentions of the speaker who performed a given speech act. Consider the following dialogue between John and Ann.

John The warehouses are valuable architecturally.
Ann Why? I don’t think so!
John The older buildings lend the town its distinctive character.
Observe that in this dialogue we have the same reasoning structure(argument1 ) as in the previous dialogue: “The warehouses are valuable architecturally, since the older buildings lend the town its distinctive character”, however, the intentions of providing the premiseare different in the case of John and in the case of Allen. That is,John utters the premise “The older buildings lend the town its distinctive character” to argue (prove) the conclusion “The warehouses
are valuable architecturally”, while Allen utters the same premise to
explain (make understandable) the conclusion.
L3 Allen: The
warehouses
are valuable
architecturally

TA3

L4 Beth: Why?
I don’tunderstand

TA4

L5 Allen: The
older buildings
lend the town
its distinctive
characterexpl
I2 Thewarehouses
are valuable
architecturally

RA2

I3 The older
buildings lend
the town its
distinctive
characterarg
L27 John: The
warehouses
are valuable
architecturally

TA27

L28 Ann: Why?
I disagree

TA28

L29 John: The
older buildings
lend the town
its distinctive
characterFigure 2. The same reasoning structure in different contexts

Fig. 2 shows how the distinction between reasoning contexts canbe captured. Say that the moves in the dialogue between John and
Ann are represented by L27 , L28 and L29 . The passage between thosemoves are modeled by TA27 and TA28 . The fragment of the previous
dialogue (represented by L3 L4 L5 and TA3 , TA4 ) generates the reasoning structure modeled by I2 , I3 and RA2 . Since the John-Ann dialogue refers to the same reasoning structure, the nodes L27 , L28 , L29 ,TA27 and TA28 should be related to the nodes I2 , I3 and RA2 . In Fig.
2, we focus on the relation that corresponds to the intentions of argumentation and explanation. If Allen’s response to Beth’s question
was intended to explain Beth why the older buildings lend the town
its distinctive character, then the node TA4 should be linked with thenode RA2 by means of an explanatory type of YA-node (denoted as
expl in Fig. 2). On the other hand, if John’s response to Ann’s question was intended to prove Ann why the older buildings lend the town
its distinctive character, then the node TA28 should be linked with thenode RA2 by means of an argumentative type of YA-node (denoted
as arg in Fig. 2).

4

CONCLUSIONS AND FUTURE WORKIn the paper, we propose the basic framework for representing argumentation and explanation as the context of reasoning with the use of
the AIF+ language. We propose to model them as the YA-nodes thatlink together the TA-nodes and the RA-nodes. The TA-nodes correspond to the response of an interlocutor in a dialogue that consists
in giving the justification (in the case of argumentation) or explanation. The RA-nodes correspond to the reasoning structure which

originates from the interaction between interlocutors in a dialogue.
Thus, we show how illucutionary force can be used to distinguishbetween the two types of reasoning. This presents a good basis forfurther research on the subject. In particular, it would be interesting
to see how the semi-formal AIF+ specification relates to a more formal framework for argumentation and explanation, such as [2].

ACKNOWLEDGEMENTS
We gratefully acknowledge the support of EPSRC under grant
EP/G060347/1 for Floris Bex, and the support from Polish Ministryof Science and Higher Education under grant N N101 009338 for
Katarzyna Budzynska.

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