This document provides an overview of deductive and inductive reasoning. It defines what an argument is and discusses the key elements of forming arguments, including making debatable statements, using logic, and constructing thesis statements. It also explains the basic forms of deductive and inductive arguments. For deductive arguments, it covers syllogisms and their components of major premise, minor premise, and conclusion. It provides examples of valid and invalid syllogisms and discusses inductive reasoning and how it differs from deductive reasoning.

1. LIB440 Week 1
Deductive and Inductive
Reasoning
DR. RUSSELL RODRIGO

2. What is an argument?

4. What is an argument?
 An argument is not a contradiction.
 Contradiction is just the automatic gainsaying of any
statement the other person makes.
 Argument is an intellectual process.
 An argument is a connected series of statements intended
to establish a proposition.

5. Argument
 An argument tries to convince readers to think or act in a particular way.
 Advertisement
 Letter from the bank
 Travel brochure
 Movie poster
 Websites
 Campaigns etc.
 An argument is not a fight. It does not need to involve conflict.

6. Debatable statement
 Your claim about the issue you are writing about should be debatable.
 Debatable = possible to (dis-)agree with
 Are the following claims debatable? (D / ND)
1. Cigarettes are taxed.
2. The tax on cigarettes should be increased.
3. I don’t like cigarettes.
4. Smoking is harmful to people’s health.
5. It is necessary for the government to increase their anti-smoking ad campaigns.
6. Some animals are endangered.
7. Endangered animals are more beautiful than animals that are not endangered.
8. Hunting endangered animals must be banned.

7. Using logic to argue your debatable
statement
 Deductive arguments
 General premise / Assumption -> Conclusion
 Traditional logic
 Deduction: all statements in an argument are true -> Conclusion must be true
 Inductive arguments
 Individual Observation (Evidence) -> Conclusion
 No strict form
 Induction: all relevant evidence stated -> Conclusion must fit the evidence
better than another conclusion would

8. Thesis Statement
 summarizes the main point of the essay.
 It is normally a single sentence found at
the end of the paper's introductory
paragraph.
 It acts as a guide to let your audience
know the central idea of the essay and to
know what to expect in the body of your
paper.

9. How to write a thesis statement
 One method of writing a thesis statement comes in the form of
“X is Y because Z.”
 "X" is your main subject
 "Y" describes your main subject
 "Z" provides the reasons about the description.
 For example
 Fast food negatively effects our health because of its many
processed ingredients.

11. Syllogisms
 The basic form of a deductive
argument is a syllogism.
 A syllogism consists of a major premise,
which is a general statement; a minor
premise, which is a related but more
specific statement; and a conclusion,
which is drawn from those premises.
 Deductive arguments should be valid
and sound.
 Premise should be true (= sound)
(unsound = a false premise).
 The conclusion should be correct
based on the premises (= valid)
(invalid cannot never be sound).
Major premise
Minor premise
Conclusion

12. What do you think of the following logical arguments?
Are they sound? valid?
1. All humans are mortal. Russell is human. Therefore, Russell is mortal.
2. No reptiles have fur. A snake is a reptile. Therefore, a snake does not
have fur.
3. Venom is dangerous. Some snakes are venomous. Therefore, some
snakes are dangerous.
4. All birds can fly. A mosquito can fly. Therefore, a mosquito is a bird.
5. No dogs can fly. A penguin is not a dog. Therefore, a penguin can fly.

13. What do you think of the following logical arguments? Are they
sound? valid?
6. All birds can fly. An ostrich can fly. Therefore, an ostrich is a bird.
7. All birds can fly. A penguin is a bird. Therefore, a penguin can fly.
8. No fish can fly. Some animals can fly. Therefore, some animals are not fish.
9. Joe is a student at Stamford. Therefore, Joey needs to pass LIB440.
10. All penguins are black and white. Old TV shows are black and white.
Therefore, penguins are old TV shows.

15. Other kinds of syllogisms
 I will either give you dog or a cat. I didn’t give you a
cat. Therefore, I will give you a dog.
 If you are a good boy, you will get a dog. You have
been a good boy. Therefore, you will get a dog.
 If you eat ice cream every day, you might become
overweight. Russell does not ice cream every day.
Therefore, Russell will not become overweight.

16. Inductive reasoning
 Induction has no distinctive form, and its conclusion is less definitive than
those of syllogisms.
1. Decide on a question to be answered, or a tentative answer to the question (= a
hypothesis).
2. Gather the evidence that is relevant to the question and helps you find the answer.
3. Move from your evidence to the conclusion (= making an inference – a statement
about the unknown based on the known).
 Danger: jumping to a conclusion!
 Jumping to conclusion: This cat is black. That cat is black. A third cat is black.
Therefore all cats are black.
 More obvious conclusion: There is a baseball on the living-room floor. The children
were playing baseball this afternoon. They are not here anymore. Therefore, one of
the children hit or threw the ball through the window; then, they all ran away.

17. Reading: inductive or deductive?
 Read the article you were assigned.
 Decide whether the author uses inductive or deductive reasoning.
 For inductive reasoning answer these questions:
 What is the hypothesis?
 What evidence is presented?
 Is the conclusion believable based on the evidence presented?
 For deductive reasoning answer these questions:
 What assumptions does the writer make?
 What conclusions does he draw?
 Is his reasoning valid and sound?
 Can you construct syllogisms based on the reasoning the writer uses?
1. No, Donald Trump Is Not a Racist. (Huffington Post Blog)
2. Is Donald Trump a Racist? (New York Times Opinion Pages)

18. Write your own syllogisms
 Base yourself on the topic in your diagnostic writing.
 Remember: