1 / 12

Valid and Invalid Arguments

Valid and Invalid Arguments. Section 1.6. Arguments. If a number is divisible by 8, then it is divisible by 4. 61 is not divisible by 4. 61 is not divisible by 8. Therefore symbol. Conclusion. Premises.

lacy
Télécharger la présentation

Valid and Invalid Arguments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Valid and Invalid Arguments Section 1.6

  2. Arguments • If a number is divisible by 8, then it is divisible by 4. • 61 is not divisible by 4. • 61 is not divisible by 8. Therefore symbol Conclusion Premises

  3. **The validity of an argument is determined by the logical form, not by whether the conclusion is true or false. • There are three valid forms that we will learn about today: • Law of Detachment • Law of Transitivity • Law of Indirect Reasoning

  4. Law of Detachment • If P then Q • P • Q • Example: Notice how P is Detached from Q

  5. Law of Transitivity • If p then q • If q then r • if p then r • Example: If Jamie gets an animal, she will get a dog. • If Jamie gets a dog, it will be a poodle. • If Jamie gets an animal, she will get a poodle. Remember the transitive property Of equality? A = B, B = C, so A = C

  6. Law of Indirect Reasoning • If p then q • Not q • not p • Example: • If it is sunny, I will wear sunglasses. • I did not wear sunglasses. • It was not sunny.

  7. Which type of reasoning is this?What conclusion can be determine? • If the moonflowers are blooming, then it is nighttime. It is daytime. • If a polygon is regular, all its sides are congruent. The sides of P are not all congruent. • If it’s Sunday, then Teri reads the comics. Teri reads the comics. Law of Detachment; the moonflowers are not blooming. Law of Indirect Reasoning; The polygon is not regular.

  8. Warning!!! They will try to Trick you!!!

  9. If it’s Sunday, then Teri reads the comics. Teri reads the comics. • P  Q • Q • P? • This is called a converse error, making the statement invalid.

  10. Another Invalid form.. Inverse Error • If we go to the movies, we will see an action movie. • We did not go to the movies. • We did not see an action movie. p  q ~p ~q ?

  11. Last Invalid Form… • On July 1st, it rained. • On July 2nd, it rained. • On July 3rd, it rained. • it rains the entire month of July. • This is called “improper induction”  you are jumping to a conclusion!

  12. Homework Page 51 – 54 2- 28 (evens)

More Related