Dialectical trade-offs in the design of protocols for computer-mediated deliberation

Ideal models of dialectical argumentation, such the pragma-dialectical critical discussion or Walton and Krabbe's persuasion dialogues, comprise of a set of rules that define reasonable argumentation under idealised conditions. Assuming such conditions, dialectical rules are meant to secure an orderly procedure for testing opinions. However, in actual circumstances violations of argumentative rules - identified as fallacies - can and do occur. Pragma-dialectics treats fallacies as "derailments of strategic manoeuvring", that is, contraventions of dialectical rules for a critical discussion committed by actual arguers for rhetorical gains. Hence, the predicament of actual argumentation is a possible (but not necessary) trade-off between dialectical constraints and rhetorical opportunities. In this paper I preliminarily conceptualise a different predicament that actual arguers may face. The sets of dialectical rules proposed in ideal models of argumentation are consistent and thus unproblematic, as long as they presuppose idealised conditions. However, when put to work in actual procedures for argumentation, the rules may clash with one another. For instance, the freedom to unlimitedly criticise the opponent may hinder the progress towards rational resolution of a difference of opinion. As a result, arguers may face a predicament in which the only way to observe one of the rules of reasonable argumentation is to violate another one. I call such possible clashes dialectical trade-offs, because they are clashes between dialectical rules that arise in actual circumstances of argumentation. Dialectical trade-offs are practical concerns that do not undermine the general composition and usefulness of the ideal models. Yet, they point to a practical difficulty in designing consistent and applicable protocols for reasonable argumentation. I will illustrate this difficulty by contrasting two kinds of protocols for computer-mediated deliberation: Internet forums for informal deliberation and formal models of deliberative dialogues developed within the field of Artificial Intelligence.