How We Argue: Inductive and Deductive Reasoning - PowerPoint Presentation

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How We Argue: Inductive and Deductive ReasoningSlide2

Lecture Outline

Inductive Reasoning

Generalizations

Cause and Effect

Analogy

Deductive Reasoning

Syllogism

EnthymemeSlide3

Inductive ReasoningSlide4

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.Slide5

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 theorySlide6

Generalizations: How To Evaluate

Is the data any good?

Is it relevant?

Is it sufficient?

Is it trustworthy?

What could be wrong?Slide7

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.”Slide8

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

. Slide9

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?Slide10

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.Slide11

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

. Slide12

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?Slide13

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”Slide14

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

.’Slide15

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:Slide16

Deductive ReasoningSlide17

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. Slide18

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. Slide19

Syllogism ExampleCan 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. Slide20

Syllogism Example

Can you find the syllogism in this ad?Slide21

Syllogism Example Can you find the syllogism in

Andrew Marvell’s “To His Coy Mistress”? Slide22

Syllogism Example Can you find the syllogisms in Susan B. Anthony’s speech?Slide23

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…Slide24

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. Slide25

Enthymeme TaskIn 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.Slide26

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!Slide27

A (Very) Brief History of ArgumentationSlide28

A (Very) Bad Math Formula for Understanding ToulminSlide29

Toulmin <–> Induction/Deduction