Review Deductive Logic Wk2 Day 2 Checking Validity of Deductive Argument Steps: 1.Rephrase as a syllogism Identify premises and conclusion. Look out for unstated premises. Place them in order P(1), P(2), C. Turn all claims into standard-form claims (keep all three terms the same!). 2.Choose your weapon Venn Diagrams Rules for Testing Validity
Deductive Arguments Training Exercise #4: Check the validity of an argument using the Rules for Testing Validity (method #2). Example: All chicken bones are things dogs can choke on. No things dogs could choke on are things you should give to dogs. So, no chicken bones are things you should give dogs. All B are C No C are G No B are G Rules for Testing Validity: 1. 1 in premise and 1 in conclusion. 2. C is distributed in premise #2. 3. B is distributed in premise #1, and G is distributed in premise #2. Valid! All rules are satisfied.
Deductive Arguments Group Training! Time for Rules Testing combat practice. Using the Rules for Testing Validity method, test to see if these are valid arguments. 1. All forms of coffee are stimulants. It s obvious since all caffeinated drinks are stimulants and all coffees have caffeine. 2. All educated people respect books, but some bookstore personnel are not truly educated. So some bookstore personnel don t respect books. 3. No islands are part of the mainland and Hawaii is an island. Therefore, Hawaii is not on the mainland.
Deductive Arguments Group Training! Time for Rules Testing combat practice. #1 All caffeinated drinks are stimulants. All forms of coffee are caffeinated drinks. All forms of coffee are stimulants. All CD are S All C are CD All C are S Rules for Testing Validity: 1. 0 in premise and 0 in conclusion. 2. CD is distributed in premise #1. 3. C is distributed in premise #2. Valid! All rules are satisfied.
Deductive Arguments Group Training! Time for Rules Testing combat practice. #2 All educated people are people who respect books. Some bookstore personnel are not educated people. Some bookstore personnel are not people who respect books. All E are R Some B are not E Some B are not R Rules for Testing Validity: 1. 1 in premise and 1 in conclusion. 2. E is distributed in premise #1 & #2. 3. R is distributed in conclusion, but not in any premise. Not valid! Rules #3 is not satisfied.
Deductive Arguments Group Training! Time for Rules Testing combat practice. #3 No islands are parts of the mainland. All Hawaiis are islands. No Hawaiis are parts of the mainland. No I are M All H are I No H are M Rules for Testing Validity: 1. 1 in premise and 1 in conclusion. 2. I is distributed in premise #1. 3. H is distributed in premise #2. Valid! All rules are satisfied.
Deductive Arguments Do The Homework Using Rules Testing Method Exercise 8-12 #3, 5, 6, 8, 9
Deductive Arguments Exercise 8-12 #3 HW Review No prescription drugs are drugs that can be taken without a doctor s order. All OTC drugs are drugs that can be taken without a doctor s order. No OTC drugs are prescription drugs. No P are WDO All OTC are WDO No OTC are P Rules for Testing Validity: 1. 1 in premise and 1 in conclusion. 2. WDO is distributed in premise #1. 3. OTC is distributed in premise #2, P is distributed in premise #1. Valid! All rules are satisfied.
Deductive Arguments HW Review Exercise 8-12 #5 Some compact disc players are players that use 24x sampling. No players that use 24x sampling are players that cost under $20. Some compact disc players are not players that cost under $20. Some CD are 24x No 24x are <$20 Some CD are not <$20 Rules for Testing Validity: 1. 1 in premise and 1 in conclusion. 2. 24x is distributed in premise #2. 3. <$20 is distributed in premise #2. Valid! All rules are satisfied.
Deductive Arguments HW Review Exercise 8-12 #6 All things that Bob won are things that Pete won. All things that Bob won are junk. All things that Pete won are junk. All B are P All B are J All P are J Rules for Testing Validity: 1. 0 in premise and 0 in conclusion. 2. B is distributed in both premises. 3. P is distributed in conclusion, but not in any premise. Not valid! Since rule #3 not satisfied.
Deductive Arguments HW Review Exercise 8-12 #8 No off-road vehicles are vehicles allowed in the... park. Some off-road vehicles are not 4-wheel-drive vehicles. Some 4-wheel-drive vehicles are vehicles allowed in the... park. No O are A Some O are not 4WD Some 4WD are A Rules for Testing Validity: 1. 2 in premise, but only 1 in conclusion. 2. O is distributed in premise #1. 3. Nothing distributed in conclusion. Not valid! Rule #1 is not satisfied.
Deductive Arguments Exercise 8-12 #9 HW Review Some people affected by the drainage tax are residents of the county. Some residents of the county are people paying the sewer tax. Some people paying the sewer tax are people affected by the drainage tax.. Some DT are R Some R are ST Some ST are DT Rules for Testing Validity: 1. 0 in premise and 0 in conclusion. 2. R is not distributed. 3. Nothing distributed in conclusion. Not valid! Rules#2 is not satisfied.
Types of Arguments Deductive Argu.: Valid or Invalid Prem.: Prove Argument Conc.: Necessarily True? Certainty/Gauranteed Inductive Argu.: Stronger or Weaker Prem: Support Argument Conc.: Likelihood? Probability
How do you evaluate? Deductive 1.Venn Diagrams 2.Syllogism Rules 3. Imagine otherwise Inductive? Depends on the type of inductive argument.
Inductive Arguments: Main Idea Extends what we have already observed to things or situations we have not observed Ex: The dog has barked at me for the last three mornings, so I think he will bark at me this morning. Others?
Types of Inductive Arguments 1. Inductive Syllogisms (General to Specific) 3. Arguments from Analogy 2. Inductive Generalization (Specific to General)
Inductive Argument: 1. Inductive Syllogisms Example: I ve got a date with Quasimodo on Sunday. Never met her, but she s probably good looking because most De Anza students are good looking. P1:Most De Anza students are good looking. UP2: Quasimodo is a De Anza student. C: Quasimodo is good looking. How do you evaluate strength of argument? Most the size of the proportion/percent. 17
Inductive Arguments: 1. Inductive Syllogisms The most are Argument (From general specific) Example: Most De Anza students are good looking. Quasimodo is a De Anza student. Quasimodo is good looking. The more most means the stronger the argument. 18
Inductive Arguments: 2. Inductive Generalization What do these statements have in common? I avoid philosophy courses. They are too hard for me. Drivers on highway 101 are crazy during rush hour. They are making a generalized statement ( feature ) about a population, based on a sample. 19
Inductive Arguments: 2. Inductive Generalization The based on the sample Argument (From specific general) I avoid philosophy courses. They are too hard for me. Drivers on highway 101 are crazy during rush hour. They are making a generalized statement ( feature ) about a population, based on a sample. 20
Inductive Arguments: 2. Inductive Generalization Example: I avoid philosophy courses. They are too hard for me. Generalization: Arriving at a conclusion about a population by looking at just a sample of it. Population (or Target or Target Population ): An entire group we are concerned with. Sample: A subset of the population. Feature: What we are generalizing 22 about the population.
Inductive Arguments: 2. Inductive Generalization Science is based on inductive generalization. How do we know that A new cancer drug works A new technique for raising children A weight loss shake works Can t test everyone. So study a sample and then generalize for the rest of us. 23