Rhetoric: Communication Techniques
Three Modes of Persuasion
Qualitative/Quantitative
September 2011
Three Artistic Proofs
Aristotle believed the goal of argumentative writing is to
persuade to your audience that your ideas are valid, or more
valid than someone else’s
 Aristotle divided the means of persuasion, also know as three
artistic proofs, into three categories:
 Ethos
 Pathos
 Logos
Wikipedia
Ethos
Ethos (Credibility), or ethical appeal
 Convincing by the character of the author – we tend to
believe people whom we respect
Wikipedia
Ethos
 One of the central problems of argumentation is to project
an impression to the reader that you are someone worth
listening to
 In other words making yourself as author into an authority on
the subject of the paper, as well as someone who is likable and
worthy of respect
Wikipedia
Logos
Logos (Logical)
 Persuading by the use of reasoning
 This will be the most important technique we will study, and
Aristotle's favorite
 We'll look at deductive and inductive reasoning, and
discuss what makes an effective, persuasive reason to back up
your claims
Wikipedia
Logos
 Deductive reasoning: constructs or evaluates deductive
arguments
 Deductive arguments: show that a conclusion necessarily
follows from a set of premises; deductive argument is valid if
the conclusion does follow necessary premises
 Example:
All men are mortal
Socrates is a man
Therefore, Socrates is mortal
Wikipedia
Logos
 Inductive reasoning: is a kind of reasoning that constructs or
evaluates propositions that are abstractions of observations
 A form of reasoning that makes generalizations based on
individual instances
 Example: 90% of humans are right-handed.
Joe is a human.
Therefore, the probability that Joe is right-handed is 90%.
Wikipedia
Logos
 Giving reasons is the heart of argumentation
 We'll study the types of support you can use to substantiate
your thesis, and look at some of the common logical fallacies,
in order to avoid them in your writing
Wikipedia
Pathos
 Language choice affects the audience's emotional response,
and emotional appeal can effectively be used to enhance an
argument
 Remember “tragic” from 8 Is Not Hate:The Meaning of a
Proposition
Wikipedia
Qualitative
 The word qualitative refers to descriptions or distinctions
based on some quality or characteristic rather than on some
quantity or measured value.
Quantitative
 The term quantitative refers to a type of information
based in quantities or else quantifiable date (objective
properties)