LOGICS FOR DIALOG
In the second half of the 20th century, various systems of logic were constructed to provide formal representations of argumentative dialogue.
— In addition to his historical account, discussion and critique of the “standard treatment of fallacies” Charles L. Hamblin (1970 proposed a “formal dialectic.”
— Paul Lorenzen and Kuno Lorenz developed a dialogical logic (Lorenzen, Lorenz, 1978).
— Else Barth and Jan L. Martens constructed a formal dialectic for analyzing arguments (Barth, Martens, 1977).
— Jaakko Hintikka (1981) studied the semantics of questions, and the logic of information-seeking dialogues.
— Building on Hamblin’s work, Douglas Walton and John Woods developed logical approaches to fallacies (Woods and Walton 1989) and to argumentative dialogues (Walton 1989).
— Lorenzen and the Erlangen School developed dialogical logic (Dialogische Logik) as a contribution to formal logic. This model was extended to include the definition of rational dialogue, and is a precursor of the pragma-dialectic approach to argumentation.
1. Logical dialogical game
The logical contribution is a method of defining logical connectives not by the traditional method of truth tables, but by means of allowed or forbidden moves in a “dialogical game.” Consider, for example, the conjunction “&”, read “and”. It can be defined using the truth table method, see logical connectives. In dialogical games, “&” is defined by the following moves:
(a) First round:
Proponent: P & Q
Opponent: Attacks P
Proponent: Defends P.
If the proponent successfully defends P, he wins round (a). If the defense fails, the game is over, and the proponent has lost. In the language of truth tables, this corresponds to the truth table line « If P is false, then the conjunction ‘P & Q’ is false ». In other words, the line “if P is false, then the conjunction ‘P & Q’ is false” is excluded.
If the proponent wins round (a), with respect to P, the game continues.
(b) Second round, the opponent attacks Q.
Proponent: P & Q
Opponent: Attacks Q
Proponent: Defends Q.
If the proponent successfully defends Q, he wins round (b). Since he already won round (a), he wins the game. If the defense fails, the game ends, and the opponent wins it.
In the language of truth tables, this means that “P & Q” is true when the proponent wins; and “P & Q” is false when the opponent wins.
2. Dialogical Logic Rules and Pragma-Dialectical Rules
Dialogical logic uses three types of rules (van Eemeren et al. 1996, p. 258).
— Starting rule: the proponent begins by asserting a thesis.
— General rules about legal and illegal moves in dialogue (see above).
— Closing rule, or winning rule, which determines who has won the game.
Similar rules apply in Pragma-Dialectics, see Rules
— The starting rule corresponds to “Rule 1. Freedom — The parties must not interfere with the free expression or questioning of points of view” »(van Eemeren, Grootendorst, Snoeck Henkemans 2002, pp. 182–183).
— The closing rule, or the winning rule corresponds to « Rule 9. Closing — If a point of view has not been conclusively defended, the advancing party must withdraw it. If a point of view has been conclusively defended, the other party must withdraw the doubts it has expressed with respect to that point of view” (ibid.).
The other rules are intended to ensure the smooth progression of an argumentative dialogue in ordinary language aimed at resolving differences of opinion.
3. A contribution to the theory of rationality
In a work entitled Logical Propaedeutic: Pre-School of Reasonable Discourse ([1967] / 1984), Kamlah and Lorenzen aim to provide “the building blocks and rules for all rational discourse” (quoted in van Eemeren et al. 1996, p. 248). Their basic assumption is that,
in order to prevent them from speaking at cross-purposes in interminable monologues, the interlocutors’ linguistic usage in a discussion or conversation must comply with certain norms and rules. Only when they share a number of fixed postulates with respect to linguistic usage can they conduct a meaningful discussion” (van Eemeren et al. 1996, p. 253).
The goal of the endeavor is to construct of an “ortholanguage” (Lorenzen & Schwemmer, 1975, p. 24; quoted in van Eemeren & al. 1996, p. 253), that defines rational dialogical behavior capable of resolving interindividual contradictions.
This approach differs significantly from the interactional approaches to speech in interaction that began developing around the same time.