Professors of Philosophy or Mathematics have long thought of formal logic as a pure, logical process using deductive reasoning and precisely defined premises and terms to come to an airtight, unassailable, syllogistic conclusion. There is no place for inductive argument, analogy, humor, or charisma in such a process. Professors of Philosophy call such argument a syllogism.
Trudy Govier, and thus this series, does not focus on syllogism.
A Practical Study of Argument, by Trudy Govier, studies a new kind of theory of argumentation that has been developing since the 1970s: Informal Logic. Where logical argument had long been restricted to syllogism, this new style of argumentation is based on the way people discuss and dispute contentious topics in real life using sentences composed of natural (non-technical) vocabulary. It also applies to litigation, advertising, and other persuasive activities.
Venn diagrams and boolean logic are not of too much importance within the realm of informal logic. Nor is Truth the ultimate measure of success. Rather, the validity of an argument is determined by whether the audience agrees with it. And an argument can be strong because of facts and evidence, or it can be strong because it is congruent with the existing beliefs and prejudices of the audience, or strong because of positive feelings and emotions solicited by the arguer as she presents her argument.
This does not mean there is no structure to informal logic. There are standard structures for informal argument, and as demonstrated in What is or isn’t an Argument there are words and grammatical structures (indicators) that reveal the existence of an argument.
Just as a teaser, here are a few pictures of standard argument structures to be used in informal logic.
This article is part of the Ars Argumentorum Series
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