Arguments and Reasoning

Argument

Monty Python – Argument Clinic video

Monty Python

Premises + Conclusion = Argument

Argument – a group of statements including one or more premises and a conclusion

Premise – a statement in an argument that provides reason or support for the conclusion

Conclusion – a statement that says what the argument is trying to prove

Argument example

Cats with long hair shed all over the house so you should not get a long-haired cat. I have heard that they also have lots of fleas.› Premise 1:Long-haired cats shed all over

the house › Premise 2: Long-haired cats have a lot of

fleas › Conclusion: You should not get a long

haired cat

Implied premises

Premises are not always directly stated, sometimes they are implied

Example:› Of course he is dumb, he is a human.› Premise 1: He is a human.› Premise 2 (implied): All humans are dumb.› Conclusion: He is dumb.

Reasoning

We use reasoning to figure out problems.

Inductive Reasoning

Inductive reasoning – conclusions are drawn based on limited information› Educated guess

Example:› 2,4,6,8,10

What comes next in the sequence?› If a child puts his or her hand into a bag of

candy and withdraws three pieces, all of which are red, he or she may conclude that all the candy is red.

Inductive Reasoning

Observation: Tonya is seen walking from her car to her home with a set of golf clubs.

Observation: Tonya’s husband Jeff loves golf and tomorrow is his birthday.

Conclusion (inference): Tonya has bought the set of golf clubs for Jeff.

Deductive Reasoning

Deductive reasoning – conclusions are drawn based on logic and fact

› Science: If… then… statements are how you test hypotheses

› If it is snowing outside, then the temperature must be near freezing.

Deductive Reasoning

Known Fact: The cut-off date for swim camp registration is June 15. After that date, kids go on a wait list - no exceptions allowed.

Known Fact: You have missed the cut-off to date to register your child by two days.

Conclusion: Your child won’t be registered and her name will go on the wait list.

Inductive vs. Deductive

Inductive reasoning can sometimes lead to FALSE conclusions

BUT it is a good first step in applying deductive reasoning to determine whether a conclusion is true.

What??› In math, you sometimes solve problems

through inductive reasoning (educated guess) and then check your answer (deductive reasoning).

Inductive Arguments

Inductive: moves from the specific to the general› Small to big› Example:

All crows I have ever seen are black. Therefore, all crows are black.

All ice I have ever touched is cold. Therefore, all ice is cold.

Inductive Arguments

Sometimes inductive arguments can lead to a false conclusion, making it an INVALID argument. › Ex:› Some dogs are ill-behaved.› All dogs are animals.› Therefore, all animals are ill behaved.

Deductive Arguments

Deductive: begins with the general and ends with the specific› Big to small› Example

All men are mortal. My father is a man. Therefore, my father is a mortal.