# Ph 21 Logic

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### Notes, Etc. :

Notes, Etc. 1. Reading for today: Argument. For Monday: None. 2. Class webpage: www.csus.edu/indiv/f/freelove on the webpage . . . syllabus Argument reading assignment list class info 3. I'll post slides used in class to class webpage.

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Two important activities of the course . . . 1. Identifying arguments. 2. Evaluating arguments.

I. Arguments

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. An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises.

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. An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises. Maria says, "Catherine is a student at State U. All students at State U. own computers. So, Catherine owns a computer.

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. An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises. Maria says, "Catherine is a student at State U. All students at State U. own computers. So, Catherine owns a computer. conclusion

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. An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises. Catherine is a student at State U. All students at State U. own computers. So, Catherine owns a computer. conclusion premise premise

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. An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises. (1) Catherine is a student at State U. (2) All students at State U. own computers. ----------------- (3) Catherine owns a computer. conclusion premise premise "standard form"

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II. Identifying Arguments

### Common Indicator Words :

Common Indicator Words

### Common Indicator Words :

Common Indicator Words conclusion indicators hence thus so therefore consequently in conclusion

### Common Indicator Words :

Common Indicator Words conclusion indicators hence thus so therefore consequently in conclusion premise indicators for since because for the reason that given that

### Common Indicator Words :

Common Indicator Words conclusion indicators hence C(onclusion) thus C so C therefore C consequently C in conclusion C premise indicators for P(remise) since P because P for the reason that P given that P

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq."

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq." conclusion indicators hence thus so therefore consequently in conclusion premise indicators for since because for the reason that given that

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq." Either Saddam shipped his WMD out of Iraq, premise or else they are still in Iraq. Saddam's WMD were shipped out of Iraq. conclusion inference bar

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq." Either Saddam shipped his WMD out of Iraq, premise or else they are still in Iraq. Saddam's WMD are not in Iraq. premise Saddam's WMD were shipped out of Iraq. conclusion inference bar

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq." (1) Either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. (2) Saddam's WMD are not in Iraq. (3) Saddam's WMD were shipped out of Iraq. "standard form"

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"Well, but look, you have to agree that Saddam shipped his WMD out of Iraq. For, either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. But, they are not in Iraq. Hence, they were shipped out of Iraq." P1. Either Saddam shipped his WMD out of Iraq, or else they are still in Iraq. P2. Saddam's WMD are not in Iraq. C. Saddam's WMD were shipped out of Iraq. "standard form"

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Maria: It's going to rain. John: It's perfectly clear outside! Why think that? Maria: Because Cody Stark on Ch. 13 forecasts rain for tomorrow, and he never gets it wrong.

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Maria: It's going to rain. John: It's perfectly clear outside! Why think that? Maria: Because Cody Stark on Ch. 13 forecasts rain for tomorrow, and he never gets it wrong. conclusion indicators ??? premise indicators ???

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Maria: It's going to rain. John: It's perfectly clear outside! Why think that? Maria: Because Cody Stark on Ch. 13 forecasts rain for tomorrow, and he never gets it wrong. conclusion indicators hence thus so therefore consequently in conclusion premise indicators for since because for the reason that given that

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Maria: It's going to rain. John: It's perfectly clear outside! Why think that? Maria: Because Cody Stark on Ch. 13 forecasts rain for tomorrow, and he never gets it wrong. Cody Stark on Ch. 13 forecasts rain for tomorrow. premise Cody Stark never gets the weather wrong. premise ---------------------

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Maria: It's going to rain. John: It's perfectly clear outside! Why think that? Maria: Because Cody Stark on Ch. 13 forecasts rain for tomorrow, and he never gets it wrong. Cody Stark on Ch. 13 forecasts rain for tomorrow. premise Cody Stark never gets the weather wrong. premise --------------------- It's going to rain. conclusion

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"The flight from Orange County arrives at 3:00 pm. Your rental car will be available at 2:50. The key is available at the Hertz counter."

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"The flight from Orange County arrives at 3:00 pm. Your rental car will be available at 2:50. The key is available at the Hertz counter." conclusion indicators hence thus so therefore consequently in conclusion premise indicators for since because for the reason that given that

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"The flight from Orange County arrives at 3:00 pm. Your rental car will be available at 2:50. The key is available at the Hertz counter."

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"The flight from Orange County arrives at 3:00 pm. Your rental car will be available at 2:50. The key is available at the Hertz counter." An argument is set of propositions, one of which, the conclusion, is taken by someone to be supported by the rest, the premises.

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"Catherine owns a computer, since all students at State U. own computers."

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"Catherine owns a computer, since all students at State U. own computers." conclusion indicators hence thus so therefore consequently in conclusion premise indicators for since because for the reason that given that

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"Catherine owns a computer, since all students at State U. own computers." All students at State U. own computers. premise ------------------------------

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"Catherine owns a computer, since all students at State U. own computers." All students at State U. own computers. premise ------------------------------ Catherine owns a computer. conclusion

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"Catherine owns a computer, since all students at State U. own computers." Catherine is a student at State U. "hidden premise" All students at State U. own computers. premise ------------------------------ Catherine owns a computer. conclusion

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III. Evaluating Arguments

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argument deductive inductive

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Argument Soundness A good deductive argument is a "sound" argument. An argument is sound, if, and only if, it satisfies the following two conditions, (i) it is valid (ii) all of its premises are true.

### Condition (i): Validity:

Condition (i): Validity An argument is valid, if and only if, IF the premises are true, then the conclusion must be true.

### Condition (i): Validity:

Condition (i): Validity An argument is valid, if and only if, IF the premises are true, then the conclusion must be true. All dogs are mammals. All mammals are warm-blooded. ------------ All dogs are warm-blooded.

### Condition (i): Validity:

Condition (i): Validity An argument is valid, if and only if, IF the premises are true, then the conclusion must be true. All dogs are cats. All cats fly. --------- All dogs fly.

### Condition (i): Validity:

Condition (i): Validity An argument is valid, if and only if, IF the premises are true, then the conclusion must be true. All mammals are dogs. Some dogs fly. --------- All mammals fly.

### Condition (i): Validity:

Condition (i): Validity An argument is valid, if and only if, IF the premises are true, then the conclusion must be true. California is a US state. The Chicago Bears are in the Super Bowl. ---------- Two plus two equals four.

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1. Either Saddam shipped his WMD out of Iraq, or the WMD are still in Iraq. 2. The WMD are not in Iraq. --------------- 3. Saddam shipped his WMD out of Iraq.

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An argument is valid, if and only if, IF the premises are true, then the conclusion must be true. 1. All space aliens have big noses. 2. Mack has a big nose. ---------- 3. Mack is a space alien.

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1. Either Saddam shipped his WMD out of Iraq, or the WMD are still in Iraq. 2. The WMD are not in Iraq. --------------- 3. Saddam shipped his WMD out of Iraq.

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An argument is valid, if and only if, it is not possible the premises are true and the conclusion is false. (1) If a student in the class studied hard, then she got an A. (2) Susan, a student in the class, got an A. ----------------- (3) Susan studied hard.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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Every skier loves some snowboarder. Josh is a snowboarder. ----------------- Picabo Street loves Josh.

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An argument is sound, if, and only if, (i) it is valid (ii) all of its premises are true.

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An argument is sound, if, and only if, (i) it is valid and (ii) all of its premises are true. 1. Osama bin Laden is a human being. 2. All human beings are mortal. ------------- 3. Osama bin Laden is mortal.

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An argument is sound, if, and only if, (i) it is valid and (ii) all of its premises are true. (1) All French Prime Ministers love the U.S.A. (2) President Bush is a French Prime Minister. ----------------- (3) President Bush loves the U.S.A.