Logic and Logical Fallacies

A.P. English Language

Today’s Learning Goals

• You should understand the difference between inductive and deductive reasoning.

(Where are you on our scale of 1 – 4?)

• You should understand the basic formation of logical fallacies.

(Where are you on our scale of 1 – 4?)

• You should be able to identify and develop examples of selected logical fallacies.

(Where are you on our scale of 1 – 4?)

Induction

• Moves from a number of particular cases to a general conclusion, wherein all instances of that type being investigated will conform.

• Inductive reasoning goes from a specific instance to a broader, more general instance.

• Inductive reasoning looks like:

Examples of Induction

• Every life form we know of depends on liquid water to exist. (Therefore) All life depends on liquid water to exist.

• Alex is a girl with a funny laugh. (Therefore) All girls must have a funny laugh.

NOTICE THAT BOTH SETS OF REASONING GO FROM A SPECIFIC INSTANCE TO A MORE GENERAL

STATEMENT.

Deduction

• Involves reasoning from the general to the particular.

• We go from a general instance to a more specific instance.

• Deductive reasoning looks like:

Examples of Deduction

• Students at WPHS love wearing bright yellow shorts. Stuart is a student at WPHS; therefore, Stuart loves wearing bright yellow shorts.

• Blondes have more fun. Stephanie is a blonde; therefore, Stephanie has more fun.

NOTICE THAT BOTH SETS OF REASONING GO FROM A GENERAL PREMISE TO A MORE SPECIFIC

APPLICATION.

Deductive Reasoning and the Syllogism

• A syllogism (pronounced SILL – uh – JIZ – m) is the formula for deductive reasoning.

Major Premise: statement universally accepted as true

Minor Premise: major premise applied to a particular object or situation

Conclusion: establishes the relationship of the object to the major proposition

Syllogisms

Major Premise: All men are mortals.Minor Premise: Socrates is a man.Conclusion: Therefore, Socrates is a mortal.

Major Premise: All cats have four legs.Minor Premise: Lucky is a cat.Conclusion: Therefore, Lucky has four legs.

Quick Knowledge Check

Somewhere on your handout, answer the three questions:

1. Which type of reasoning goes from specific instances to a general instance?

2. Which type of reasoning looks like this:

3. Which type of reasoning can be flawed?

Quick Knowledge Check

Did you answer:

1. Inductive2. Deductive

3. BOTH

If you got all three correct, stand up and take a bow!

Today’s Learning Goals

• You should understand the difference between inductive and deductive reasoning.

(Where are you on our scale of 1 – 4?)

Fallacies (Falsehoods)

Logic can sometimes go awry. Even with the best of intentions, our arguments can veer off course if we don’t pay attention to the pitfalls.

You will be exposed to fifteen of the most common logical fallacies today, in order to

avoid them in your own logic and reasoning.

FALLACIES

BEGGING THE QUESTION: Assuming something to be true that really needs proof.

IGNORING THE QUESTION: A question is set up so that the argument is shifted to new ground, or an appeal is made to some emotional attitude having nothing to do with the logic in this case.

FALLACIES

EQUIVOCATION: Using the same term with different meanings.

NON-SEQUITUR: The conclusion doesn’t follow from the preceding arguments/statements.

FAULTY DILEMMA/EITHER-OR FALLACY: The major premise presents a choice that doesn’t exhaust the possibilities

FALLACIES

POST HOC ERGO PROPTER HOC: Attempts to prove that because a second event followed a first event, the second event was the result of the first.

ARGUMENTUM AD HOMINEM: Turning from the issue to the character involved.

FALLACIES

AD MISERICORDIAM: An appeal for sympathy

COMPOSITION: Arguing that a group must have the same qualities or characteristics as its members

DIVISION: Arguing that an individual must have the characteristics of the group

FALLACIES

DICTO SIMPLICITER: An argument based on an unqualified generalization

OVERGENERALIZING/HASTY GENERALIZATION: Too few instances are presented to reach an accurate conclusion

FALSE ANALOGY: Wrongful comparisons of dissimilar situations

FALLACIES

AD VERICUNDIAM: An appeal to authority

AD POPULUM: An appeal to a crowd

Today’s Learning Goals

• You should understand the basic formation of logical fallacies.

(Where are you on our scale of 1 – 4?)

Your Assignment

• You have been assigned to a group. Your group number is listed on your handout next to your name, in green ink.

• Your group will be given three logical fallacies from the list.

• Your group is to develop three examples of each assigned logical fallacy. You may not use any of my examples. You will get ten minutes to come up with examples for your assigned fallacies.

Your Assignment

• On the large sheet of lined paper, you are to neatly write the three examples that you came up with for your three logical fallacies. Refer to the handout or to the board for an example of how your sheet should be set up.

DO NOT WRITE DOWN THE ACTUAL NAME OF THE FALLACY ON YOUR PAPER!

When your group presents your examples to the class, the class and the teacher will attempt to figure out which

fallacies you were assigned.

Today’s Learning Goals

• You should be able to identify and develop examples of selected logical fallacies.

(Where are you on our scale of 1 – 4?)