Reason as WOK

• LOGIC - The process of proper reasoning & the

study of good use of arguments.

DEDUCTIVE REASONING• Deductive reasoning moves from the…..

to the ……• Deductive reasoning moves from the

general rule to the specific.• All dogs are mammals.

Chester is a dog.Therefore Chester is a mammal.

• A deductive argument is VALID if it is logically constructed or INVALID if it’s not logical. Example:

• All Italians like spaghetti.Maria likes spaghetti.Therefore Maria is Italian.

Valid or invalid?

How reliable is deductive reasoning?

• A deductive argument consists of premises/general rules & a conclusion.

• A deductive argument is always true/sound if it’s VALID and if its PREMISES are true.

• All humans are mortal. (premise)Socrates is human. (premise)Therefore Socrates is mortal.

• But how do we acquire true premises?• through observation and inductive

reasoning

Deductive reasoning in everyday use:

• In everyday use, we often don’t bother stating obvious premises, but we still use deductive arguments very commonly:

• Anna goes to Stanford, so she must be very smart. What is the unstated premise?

• Only smart people go to Stanford.• Since it’s natural to eat meat, there’s

nothing morally wrong with it. What is the unstated premise?

• Whatever is natural is also moral.• Which AOK relies most heavily on

deductive reasoning?

INDUCTIVE REASONING

• Inductive reasoning moves from the specific data to the general conclusion.

• To use the previous example… How would you come to the conclusion that humans are mortal?

• By collecting specific data that shows that humans die and also by lack of any contradictory evidence (lack of humans who have lived forever).

• Inductive reasoning relies on the coherence of data – all evidence must fit together.

Inductive reasoning in everyday use:

• Let’s play a game based on inductive reasoning…

• We use it constantly as a practical way of knowing:

• My neighbor’s dog has been friendly to me day after day. Therefore, I have accepted that it will never bite me. What is the problem with this?

• Generalizations can easily turn into stereotyping and prejudice.

• This is made worse by a phenomenon knows as confirmation bias: people tend to select and look for evidence that confirms their expectations and prejudices. Examples?

• Politics, personal looks, journalism, research, etc.

Other limitations of inductive reasoning

• It depends on observation and on our senses.

• Metal A expands when heated; metal B expands when heated; metal C expands when heated. Therefore all metals expand when heated.

• What percentage of the metal existing on our planet would you guess scientists have tested to see if it expands when heated? What does this suggest about the certainty or otherwise of scientific laws?

• Science typically formulates “laws” on the basis of a limited number of observation.

• Relying too much on the past to predict the future.

Deductive Reasoning in groups – solve “The Liar Problem” &

explain your deductive reasoning to the class.

Inductive or deductive reasoning?

• Which one moves from specific data to a general conclusion?

• Inductive• Deductive reasoning moves from

the general rule to the specific.• Your English teacher has asked

you to find examples of metaphor in the text.

• In science, you need to conduct a series of experiments to prove a hypothesis.

The dog gets excited when you get her leash out and seems to know that you are about to go for a walk. What kind of reasoning does she use?

Lateral/Creative Reasoning• Also known as “thinking outside the box” – looking

for creative solutions, outside of your current paradigm (way of thinking, basic assumptions, accepted pattern)

• Connect the nine dots below by using only 4 straight lines and without taking your pen off the paper.

Go to the next slides only if you’re ready to see some solutions to the 9-dot problem.

LOGICAL FALLACIESThey are errors in reasoning. As a speaker, you need to avoid them. As a listener, you need to be alert to recognize them. People use them when they don’t have enough sound arguments. They are illogical, and most often unethical and misleading. But they work…so they are commonly used.Why are we concerned about fallacies when it comes to knowledge and learning?Reasoning is a fundamental WOK and fallacies distort facts & obstruct sharing of knowledge.

Irrelevant Evidence (non sequitur)

• When the information has nothing to do with the argument; the conclusion does not follow from the evidence.

• Example: The merchandise at the Ultra Store is top quality, because the manager has clothes shipped in from all over the world.

• Example: My Baseball team spent more money on players than your baseball team. Therefore this means that my team is definitely better.

Emotional appeal – Argumentum ad Miscordiam

• Is a variation of “irrelevant evidence”

• My client is a good family man.• My client had a messed up

childhood.• Therefore my client is not guilty.

Argument from ignorance

• There is no proof unicorns do not exist. Therefore they do exist…

• This fallacy is also known as “Absence of proof is not proof of absence…” Why is it a fallacy?

• Because absence of proof is not proof of presence either…

• Russell’s teapot is an analogy created by Bertrand Russell to illustrate this fallacy, making the point that the burden of proof lies upon the person making a claim.

Red Herring

• Using an irrelevant issue in order to divert attention from the subject.

• The name of this fallacy comes from an old trick used in England to keep fox hunters from galloping through the crops by dragging a red herring with a strong odor along the edge of the field to distract the hounds.

• Example: Why should we worry about endangered animal species when thousands of people are killed in automobile accidents each year?

Name Calling (ad hominem)Also known as “poisoning the

well”• Is a variation of the “red herring” fallacy

• Attacking the person rather than dealing with the real issue.

• Bob says XYZ Bob is a _____ (communist, felon…) Therefore XYZ is wrong.• Example: A speaker might ask you to vote

against a candidate, not because of what he stands for, but because he is “divorced and his wife left him for a good reason.”

http://www.christianlogic.com/products/item/the-fallacy-detective/

Card Stacking

• Presenting only the facts that build the best case for your argument, ignoring completely any other facts that exist.

• Example: “Mom, I did all the dishes, I made dinner, and I put all my clothes away, so I should be allowed to stay out until midnight with my friends.” This person is using card stacking, because he ignores the facts that he broke half of the dishes, burned the dinner, and flunked all of his classes.

Slippery Slope

• Implying that taking a first step will lead to a second step and so on down the slope to disaster.

• The name of this fallacy comes from the image of taking a step down a slippery hill and tumbling down to the bottom.

• Example: If we pass laws to limit violence shown on TV, this will soon result in absolute government control of the media and total censorship. That’s communism!

• Example: You can never give anyone a break. If you do, they'll walk all over you!

Either-Or(Black or White)

• Forcing listeners to choose between only two alternatives, when many more exist in reality. Deliberately oversimplifying a complex issue to create fear.

• Example: Either we build a new high school or the children in this community will never be able to go to college.

False/Hasty Generalization

• When generalizations are based on very limited data… often due to bias.

• Example: asking one person what she thinks about gun control would clearly not provide an adequate sized sample for determining what Americans in general think about the issue.

Anecdotal Evidence is often used for hasty generalizations

• Using a few personal experiences to prove that something is true or false.

• Example: "A Volvo! You've got to be kidding. My brother-in-law had a Volvo. First, that fancy fuel injection computer thing went out. Had to replace it. Then the transmission and the clutch. Finally sold it in three years for junk."

Circular Reasoning

• Also known as “vicious cycle” or “begging the question.”

• X is true because of Y.Y is true because of X.

• Example: The Bible is the Word of God, because God tells us so ... in the Bible.

Bandwagon

• Do something that others are doing simply because others are doing it.

• Example: “Four out of five dentists preferred Crest toothpaste.”

• Example: “It’s alright for me to cheat on my taxes because everyone else does it.”

Appeal to Authority

• Tiger Woods drives a Buick.• Tiger Woods is great at golf.• Therefore Buicks are great

cars.• Similar to or variation of which

other fallacies?• Bandwagon and Irrelevant

evidence