1. Building Blocks and Application
Introduction to LOGic
Building Blocks and Application

2. PART 1: The Building Blocks
LOGIC
True
Valid
REASONING
Inductive
Deductive
SYLLOGISMS
Categorical
Hypothetical
Disjunctive

3. LOGIC
Definition of logic: Reasoning according to strict principles of validity
Other definitions to know:
Truth = Accurate, factual
Validity = Quality of arguments; proof of conclusion
Premise = A proposition used as evidence in an argument
Conclusion = Logical result of the relationship between the premises; the thesis of the argument
Argument = The assertion of a conclusion based on logical premises
Premise + Conclusion = Argument

4. REASONING Inductive = specific to general
Example: You eat at 3 Mexican restaurants, and they are all good. Based on this, you conclude that all Mexican food is good. This is inductive (3 specific examples led to a general conclusion).
Deductive = general to specific
You know the food at El Rancho will be good before you go because all Mexican food is good. This is deductive (You used your general conclusion to apply to a specific example).

5. SYLLOGISMS
Syllogism is the form in which all deductive reasoning is worked out in Aristotelian logic.
All syllogisms consist of 3 parts:
Major premise (general statement)
Minor premise (specific example)
Conclusion

6. Syllogisms and Validity/Truth
Example #1:
All cows eat grass
Bessy is a cow
Therefore, Bessy eats grass
This syllogism is _____ and _____
Example #2:
All cows are blue
Therefore, Bessy is blue

7. 3 TYPES OF SYLLOGISMS Categorical: MP is universal
Hypothetical: MP uses “if”
Disjunctive: MP uses “either/or”
* MP = Major Premise

8. Categorical Syllogism (CS) Rules
MP is universal
An entire class or category is under consideration
Universal affirmative = all, every, everyone, everybody
Universal negative = no, not, not any, never, none, nothing
For validity in a CS:
If both premises are positive, the conclusion must be positive
If one of the premises is negative, the conclusion must be negative
A conclusion cannot be drawn from 2 negative premises

9. CS EXAMPLES Fill in the blank: Fill in the blank: cows = A blue = B
Bessy = C
Fill in the blank:
______ like to chase mice.
Tinkerbell is a cat.
Therefore, Tinkerbell likes to chase mice.
A = B
C = A
Therefore, C = B
Fill in the blank:
Some celebrities are very shy.
Angelina Jolie is a celebrity.
Therefore, _____ .

10. Hypothetical Syllogism (CS) Rules
MP uses “if”
Expresses a hypothetical, uncertain, or conjectural relationship
Expresses cause and effect
“If” clause = antecedent
“Then” clause = consequent
The minor premise must either:
Affirm the antecedent, or
Deny the consequent

11. HS EXAMPLES Fill in the blank: Fill in the blank:
If someone comes to the door, the dogs will bark.
Someone came to the door.
Therefore, the dogs barked.
Fill in the blank:
If Tom asks Jen to the dance, she will go.
_____ .
Therefore, _____ .
If someone comes to the door, the dogs will bark.
The dogs did not bark.
Therefore, nobody came to the door
Fill in the blank:
If unemployment does not increase, Obama will make history.
_____ .
Therefore, _____ .

12. Disjunctive Syllogisms (DS) Rules
MP uses “either/or”
Two possibilities being proposed must be mutually exclusive
A valid DS always denies one of the disjuncts

13. DS EXAMPLES Valid: Fill in the blank: Not Valid: Fill in the blank:
He is either dead or alive.
She is either a singer or not a singer.
Fill in the blank:
Either P or Q.
Not Q.
_____ .
Not Valid:
Either you can vote Republican or bankrupt the country.
She is either a singer or a dancer.
Fill in the blank:
Either P or Q. P.
_____ .

14. MY SOAPBOX
If truth is factual accuracy, then it can’t be argued for or against.
Truth is factual accuracy.
Therefore, truth can’t be argued.
(Therefore, we argue validity.)

15. PART 2: The Application
THE ENTHYMEME
FALLACIES

16. THE ENTHYMEME
Definition: A shortened, informal syllogism in which one of the premises or conclusion is implicit.
Example syllogism:
All whales are mammals.
Moby Dick is a whale.
Therefore, Moby Dick is a mammal.
Appositive:
Moby Dick, a whale, is also a mammal.
Participial Phrase:
Being a whale, Moby Dick is also a mammal.
Prepositional Phrase:
As a whale, Moby Dick is also a mammal.
Adverb clause:
Because Moby Dick is a whale, it is also a mammal.
Compound sentence:
Moby Dick is a whale; therefore, Moby Dick is a mammal.

17. Syllogism Enthymeme Change syllogism into enthymeme:
Summers in Scotland are rainy and cool.
Edinburg is in Scotland.
Summers in Edinburg are rainy and cool.
Doctors are rich
My brother is a doctor
My brother is rich
Change syllogism into enthymeme:
Students who spend a lot of time as school are good students.
Riley spends a lot of time at school
Riley is a good student.
Snakes with triangle-shaped heads are poisonous.
Copperheads have triangle- shaped heads.
Therefore, Copperheads are poisonous.

18. Enthymeme Syllogism Change enthymeme into CS and HS:
As an athlete, Anna Sharapova is careful about what she eats.
The kangaroo, with a pouch for its young, is a marsupial.
Change enthymeme into CS and HS:
The sketches, are signed by Van Gogh; therefore, they will bring high dollars at auction.
Because Yogi is a bear, he will hibernate during the winter.

19. FALLACIES
Rhetorical fallacies don’t allow for the open, two-way exchange of ideas upon which meaningful conversations depend. Instead, they distract the reader with various appeals instead of using sound reasoning.
Rhetorical fallacies can be divided into 3 categories:
Emotional fallacies: Unfairly appeal to the audience’s emotions.
Ethical fallacies: Unreasonably advance the writer’s own authority or character.
Logical fallacies: depend upon faulty logic.
Keep in mind that rhetorical fallacies often overlap.

20. EMOTIONAL FALLACIES
Sentimental Appeals use emotion to distract the audience from the facts.
The thousand of baby seals killed in the Exxon Valdez oil spill have shown us that oil is not a reliable energy source.
Red Herrings use misleading or unrelated evidence to support a conclusion.
That painting is worthless because I don’t recognize the artist.
Scare Tactics try to frighten people into agreeing with the arguer by threatening them or predicting unrealistically dire consequences.
If you don’t support the party’s tax plan, you and your family will be reduced to poverty.
Bandwagon Appeals encourage an audience to agree with the writer because everyone else is doing so.
Paris Hilton carries a small dog in her purse, so you should buy a hairless Chihuahua and put it in your Louis Vuitton.

21. Emotional Fallacies Continued
Slippery Slope arguments suggest that one thing will lead to another, oftentimes with disastrous results.
If you get a B in high school, you won’t get into the college of your choice, and therefore will never have a meaningful career.
Either/Or Choices reduce complicated issues to only two possible courses of action.
The patent office can either approve my generator design immediately or say goodbye forever to affordable energy.
False Need arguments create an unnecessary desire for things.
You need an expensive car, or people won’t think you’re cool.

22. ETHICAL FALLACIES
False Authority asks audiences to agree with the assertion of a writer based simply on his or her character or the authority of another person or institution who may not be fully qualified to offer that assertion.
My high school teacher said it, so it must be true.
Using Authority Instead of Evidence occurs when someone offers personal authority as proof.
Trust me – my best friend wouldn’t do that.
Guilt by Association calls someone’s character into question by examining the character of that person’s associates.
Sara’s friend Amy robbed a bank; therefore, Sara is a delinquent.
Dogmatism shuts down discussion by asserting that the writer’s beliefs are the only acceptable ones.
I’m sorry, but I think penguins are sea creatures and that’s that.

23. Ethical Fallacies Continued
 Moral Equivalence compares minor problems with much more serious crimes (or vice versa).
These mandatory seatbelt laws are fascist.
Ad Hominem arguments attack a person’s character rather than that person’s reasoning.
Why should we think a candidate who recently divorced will keep her campaign promises?
Strawperson arguments set up and often dismantle easily refutable arguments in order to misrepresent an opponent’s argument in order to defeat him or her
Person A: We need to regulate access to handguns.
Person B: My opponent believes that we should ignore the rights guaranteed to us as citizens of the United States by the Constitution. Unlike my opponent, I am a firm believer in the Constitution, and a proponent of freedom.

24. LOGICAL FALLACIES
Hasty Generalization draws conclusions from scanty evidence.
I wouldn’t eat at that restaurant—the only time I ate there, my entree was undercooked.
Faulty Causality (or Post Hoc) arguments confuse chronology with causation: one event can occur after another without being caused by it.
A year after the release of the violent shoot-’em-up video game Annihilator, incidents of school violence tripled—surely not a coincidence.
Non Sequitur (Latin for “It doesn’t follow”) is a statement that does not logically relate to what comes before it.An important logical step may be missing in such a claim.
If those protesters really loved their country, they wouldn’t question the government.
Equivocation is a half-truth, or a statement that is partially correct but that purposefully obscures the entire truth.
“I did not have sexual relations with that woman.” – President Bill Clinton

25. Logical Fallacies Continued
The Gambler's Fallacy is committed when a person assumes that a departure from what occurs on average or in the long term will be corrected in the short term.
"You see that horse over there? He lost his last four races. I'm going to bet on him."
Begging the Question occurs when a writer simply restates the claim in a different way; such an argument is circular.
His lies are evident from the untruthful nature of his statements.
Faulty Analogy is an inaccurate, inappropriate, or misleading comparison between two things.
Example: Letting prisoners out on early release is like absolving them of their crimes.
Stacked Evidence represents only one side of the issue, thus distorting the issue.
Cats are superior to dogs because they are cleaner, cuter, and more independent.