1. How We Argue: Inductive and Deductive Reasoning

2. Lecture Outline Inductive Reasoning Generalizations Cause and Effect
Analogy
Deductive Reasoning
Syllogism
Enthymeme

3. Inductive Reasoning

4. Inductive Reasoning: Review
The process of citing a number of specific examples or observations to draw general conclusions.
Inductive arguments can never be 100% true. The goal is to get as close to that unobtainable number as possible. If inductive reasoning leads to a 100% truth, that truth then becomes a premise for deductive reasoning.
For example, at one point there were many theories about the spread of HIV. However, over time, inductive reasoning (the scientific method), let to the accepted claim that it can be transmitted through sex. This is now an agreed upon fact, but it wasn’t always so.

5. Inductive Reasoning: Generalization
This is the most common form of inductive reasoning, when a series of observations leads to a logical conclusion. It’s synonymous with induction.
Think “Scientific Method” – Observations lead to theory

6. Generalizations: How To Evaluate
Is the data any good?
Is it relevant?
Is it sufficient?
Is it trustworthy?
What could be wrong?

7. Generalizations: TASK
In your journal, copy the following examples of generalizations. Then, in your own words evaluate their validity.
“Professor Davis is awful. My roommate had him last year and said he can’t explain anything in simple terms.”
“Raleigh is a dangerous place. Last year alone, 13 people were murdered.”

8. Inductive Reasoning: Cause and Effect
Cause and effect arguments use inductive reasoning to hypothesize on the causes and the outcomes (effects) of particular events.
Some deductive reasoning might be used to support cause and effect arguments and some arguments are written in syllogism form; however, by nature we are guessing based on observations and patterns.

9. Cause and Effect: How to Evaluate
Does it make sense?
Are there any alternative causes?
Are their instances when the effect occurs despite the cause being absent?
Are the ideas really related?
Are the observations/patterns justified?
Is the outcome reasonable?

10. Cause and Effect: TASK
In your journal, copy the following examples of generalizations. Then, in your own words evaluate their validity.
Every morning the rooster crows before the sun rises. Hence, the rooster must cause the sun to rise.
2. Average temperatures are higher at the equator than in any other area. Individuals living at or near the equator tend to have lower per-capita incomes than individuals living elsewhere. Therefore, higher average temperatures cause lower per capita incomes.

11. Inductive Reasoning: Analogy
An analogy is a lengthy comparison. You are essentially saying that one thing (A) is similar to something else (B) because they share certain characteristics.
These characteristics are based off of observations and, thus, analogy arguments are considered a type of inductive reasoning.
Since A and B are not actually the same thing (or else we wouldn’t be making an analogy), it is safe to say that A cannot be the same as B. However, like all inductions the more similar they seem (the more characteristics they share), the stronger the inductive argument.

12. Analogy: How To Evaluate
Are the similarities strong?
Are their enough similarities?
Are the similarities relevant?
Are the similarities complex?
Are the differences irreconcilable?
Is their a counter analogy?

13. Analogy Task
You will get two analogy arguments. State the analogy claim. List the compared terms and, finally, evaluate the validity of the analogy. See document “Unit 1, Lesson 5 Evaluating Analogies”

14. Analogy: Example 1
In some ways the role of education in the development of the individual is much like the role of habitat in the natural selection of species. Earlier I made a distinction between species which have a very specialized adaptation to a very narrowly defined kind of environment, and versatile species which can survive in all sorts of conditions: the difference, say, between a rare alpine plant which can only exist at a particular altitude on the north face of a rock of a particular chemical composition, and a common garden weed. And I made the point that it is the versatile species, the weeds, which are not tied down to any particular orthodoxy, which have been the best prospect of survival in a rapidly changing world. So it is with individuals. The people who are going to be able to cope with our rapidly changing future are those who are temperamentally unorthodox – the curious, the sceptical, the ones who don’t care a fig for established opinion, people like Charles Darwin who said of himself: ‘I have steadily endeavoured to keep my mind free so as to give up any hypothesis, however much beloved, as soon as facts are shown to be opposed to it.’

15. Analogy Example 2
The whole history of bolshevism, both before and after the October revolution, is full of instances of manoeuvring, temporising and compromising with other parties, bourgeois parties included! To carry on a war for the overthrow of the international bourgeoisie, a war which is a hundred times more difficult, prolonged and complicated than the most stubborn of ordinary wars between states, and to refuse beforehand to manoeuvre, to utilize the conflict of interests (even though temporary) among one’s enemies, to refuse to temporise and compromise with possible (even though transitory, unstable, vacillating and conditional) allies – is this not ridiculous in the extreme? Is it not as though, when making a difficult ascent of an unexplored and hitherto inaccessible mountain, we were to refuse beforehand ever to move in zigzags, ever to retrace our steps, ever to abandon the course once selected to try others?
–V.I. Lenin, “Left Wing” Communism:

16. Deductive Reasoning

17. Deductive Reasoning: Overview
The process of arriving at a specific conclusion from a set of general premises. Premises are general truths, or commonplaces, that have been accepted as true (proven at one time through inductive reasoning).
If you accept premises and the argument is logical, you MUST accept the conclusion. A sound deductive argument can be considered 100% true.
Often times, qualifiers are used to make deductive arguments acceptable.

18. Syllogism
A syllogism is a nice, clean way to organize deductive arguments. Usually, there are two premises that lead to a logical conclusion.
Premise 1: Dogs are animals.
Premise 2: Bobo is a dog.
Conclusion: Therefore, Bobo is an animal.
Rarely do people actually argue using the language of syllogisms; however, nearly all arguments rely on these ideas (accepted premises and general conclusions). The better you can become at finding the deductive syllogisms presented in arguments, the easier it is to evaluate or refute arguments.

19. Syllogism Example Can you find the syllogisms in each argument?
Mom: You can’t go with your friends to Mexico for spring break. Son: But everyone is doing it. Mom: Who cares what everyone is doing. Not everyone has good parents. Son: Jeff’s parents are good and they’re letting him go.

20. Syllogism Example Can you find the syllogism in this ad?

21. Syllogism Example Can you find the syllogism in Andrew Marvell’s “To His Coy Mistress”?

22. Syllogism Example Can you find the syllogisms in Susan B
Syllogism Example Can you find the syllogisms in Susan B. Anthony’s speech?
Voting in a democracy is not wrong; I voted in a democracy; I was not wrong.

23. Syllogism
As you can see, we don’t often argue with complete syllogisms. Often times part of the syllogism is implied, or left out. That’s why we have…

24. Enthymeme
An enthymeme is an implied syllogism. It removes the obvious premise and ditches the “if-then” language. In the end, it is a fancy term for a claim and its reason.

25. Enthymeme Task In your journal, Change the following enthymeme’s into syllogisms.
Since she is from Hong Kong, she must be able to speak Chinese.
Government censorship of literature threatens our freedom of expression. It should never be adopted.
People from the south are more relaxed. She is from the south.
I studied, so I will get a good grade.
Joe and Jane broke up; I will be dating Jane soon.

26. Putting It All Together
So how are all of these things related? What do claims have to do with inductive reasoning? And where does inductive reasoning come into Toulmin’s Method?
Great Questions!

27. A (Very) Brief History of Argumentation
7th Century BC –Reasoning is alive and well. Daniel, of Biblical fame, uses inductive reasoning in his food experiment.
4th Century BC – Aristotle names things. The ancient philosopher writes the Bible of argumentation: Rhetoric. This study identifies deduction (enthymemes) as a major form of argumentation.
17th century AD – The Scientific Revolution takes off. Inductive reasoning (Scientific Method) leads to hundreds of scientific breakthroughs and boring science lessons for years to come.
20th Century AD – Stephen Toulmin takes all of these ideas and tries his best to make them useful for normal people who like to argue. His modern study introduces Toulmin’s Method.

28. A (Very) Bad Math Formula for Understanding Toulmin
Deductive Reasoning
Inductive Reasoning
Modern Arguments
Toulmin’s Method

29. Toulmin <–> Induction/Deduction
Every type of argument has a claim. This does not really change.
Claim
Inductive arguments use facts, statistics, quotes, observations for data.
Deductive arguments use premises and general truths for data.
Data
Warrants come in many forms. Some warrants are implied, many use some form of deductive reasoning to support the data (e.g. doctors are smart; he is a doctor; he is smart), and sometimes inductive reasoning could be used to support data.
Warrant