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routines and tasks (posting, editing, elaborating,
reading, attacking, etc.).
Our proposal in this context involves integrat-
ing three approaches: the IBIS approach (Issue
based information system, Conklin, 2006), the
Toulmin argument analysis structure (1959) and
the concept of argument schemes proposed by
Walton (1989, 2006). The proposed representa-
tion aims to be very close to what people usually
mean by argumentation, keeping formalization at
a minimum without losing the structuring power
of arguments.
The IBIS approach represents arguments us-
ing three basic elements: Questions, which pose
a problem or issue, Ideas, which offer possible
solutions or explanations, and pro/con Arguments,
which support or reject an idea or other argument.
In the IBIS framework arguments develop as
trees (as in Figure 3). Several software tools for
argument mapping have been developed, but their
application has largely been limited to small scale,
physically co-located groups, usually requiring
the presence of a facilitator.
According to Toulmin (1959), Toulmin, Rieke
& Janik (1979) an argument is a sequence of in-
terconnected affirmations (claims) that establish
the content and the strength of the position of the
orator (Hitchcock and Verheij, 2005). As a conse-
quence, argumentative speech can be broken down
into a series of claims. Claims can be classified
into the following categories, with respect to the
functions that they have in the speech:
Following Toumin's framework we can define
an argument as an inference mechanism (warrant)
capable of transferring the degree of truth of a set
of premises (grounds) to a conclusion.
Walton (2006) classifies arguments in three
categories: deductive, inductive, plausible
: D e d u c -
tive
arguments (modus ponens, modus tollens,
syllogism) are such that if the premises are true,
the conclusion must be true (e.g. Portland is in
Maine, Maine is in the US, then Portland must be
in the US).
Inductive
arguments are such that if
the premises are true, the conclusion is probably
true (Most American cats are domestic, Bill is
an American cat, Bill is (with high probability)
a domestic cat).
Plausible
arguments are such
that if the premises are true then a weight of
plausibility is shifted to the conclusion. Plausible
arguments are used when not all needed informa-
tion is available (or is made explicit): “To say that
a statement is plausible we mean that it seems to
be true based on the data known and observed
so far in a kind of situation we are familiar with”
(Walton, 2006: 83).
Plausible arguments can be classified into
“schemes”. Schemes represent stereotypical,
commonly-used ways of drawing inferences
(Rahwan et al., 2007) that can be considered
acceptable in absence of complete information.
Structures and taxonomies of schemes have been
proposed by many theorists, such as Perelman
and Olbrechts-Tyteca (1969). Walton's exposition
is very appealing since his classification is drawn
from the everyday use of arguments. A second
desirable characteristic of Walton's schemes is that
they are each assigned a set of critical questions
enabling contenders to identify the weaknesses
of an argument and potentially attack it (see some
examples in table 1). Compared with deductive and
inductive arguments we can say that the critical
questions can be viewed as “premises that need to
be verified”, as they are usually implicit or taken
for granted in everyday reasoning.
Walton's scheme theory could be used by
readers to recognize and classify arguments pro-
• the key
claim
, or conclusion of an argumen-
tation;
• the
grounds
, such as the facts, common
sense, and opinions of influential people
offered to support a key claim;
•
warrants
, meaning the rules that demonstrate
how the grounds support the claims;
•
qualifiers,
, which are expressions or terms
that limit the validity of the claims, such as
“usually”, “rarely”, “according to what we
know”, etc.
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