10 Answer Key for Select Exercises
Chapter 7 Deductive Arguments
Exercise 1.2
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Exercise 1.3
(b) A valid argument with all true premises and a false conclusion.
Answer: This is not possible. By definition, a valid argument with true premises must have a true conclusion.
(c) A valid argument with at least one false premise and a true conclusion.
Answer:
All birds are dogs.
All crows are birds.
Thus, all crows have bones.
(d) A valid argument with at least one false premise and a false conclusion.
Answer:
All birds are dogs.
All crows are birds.
Thus, all crows are dogs.
(e) An invalid argument with all true premises and a true conclusion.
Answer:
All birds have bones.
All dogs have bones.
Thus, all crows have bones.
(f) An invalid argument with all true premises and a false conclusion.
Answer:
All birds have bones.
All dogs have bones.
Thus, all worms are dogs.
(g) An invalid argument with at least one false premise and a true conclusion.
Answer:
All worms are dogs.
All dogs have bones.
Thus, all crows have bones.
(h) An invalid argument with at least one false premise and a false conclusion.
Answer:
All worms are dogs.
All dogs have bones.
Thus, all birds are dogs.
Chapter 2.5 Diagramming Arguments
2. (1) Linda must be home already, since (2) she got out of school early today and (3) she always goes directly home after school.
Premise indicators: since
Conclusion indicators: none
2 + 3
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1
4. (1) You should buy this car. (2) It is a great car to drive and (3) it will have a high resale value since (4) it is so popular.
Premise indicators: none
Conclusion indicators: none
4
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2 3
1
6. (1) Ticks are arachnids. (2) Arachnids have four pairs of legs, but (3) the bug you found on your arm had only three. So (4) it wasn’t a tick.
Premise indicators: none
Conclusion indicators: so
1 + 2 + 3
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4
8. I’m sure (1) you don’t have scurvy. (2) That’s a disease caused by a vitamin C deficiency, and (3) you get plenty of vitamin C, since (4) you eat so many oranges and (5) they have a lot of vitamin C.
Premise indicators: since
Conclusion indicators: none
4 + 5
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2 + 3
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1
10. (1) Either the cook or the chauffeur murdered the butler. Since (2) the cook was in town all day, (3) he could not have done it. So (4) the chauffeur must have done it.
Premise indicators: since
Conclusion indicators: so
2
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1 + 3
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4
12. (1) Anyone who lives in the desert and doesn’t own a dependable car is a fool. (2) Susan lives in the desert; (3) she is no fool, and (4) she owns a Ford Pinto. Clearly then (5) a Pinto is a dependable car.
Premise indicators: none
Conclusion indicators: clearly then
1 + 2 + 3 + 4
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5
14. (1) Judy is either a follower of Karl Marx or a follower of Groucho Marx. But (2) she can’t be a follower of Karl Marx since (3) she says that learning history is a waste of time and (4) no follower of Karl Marx would say that. So (5) she is a follower of Groucho.
Premise indicators: since
Conclusion indicators: so
3 + 4
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1 + 2
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5
16. (1) Our policy of using nuclear weapons as deterrents is a form of terrorism, for (2) the primary targets of our weapons are civilian populations, and (3) threatening the lives of innocents as a means of achieving one’s goal is terrorism. (4) Even if one’s goals are praiseworthy, one is never justified in pursuing those goals through terrorism. Therefore, (5) we are not justified in our policy of nuclear deterrence.
Premise indicators: for
Conclusion indicators: therefore
2 + 3
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17. (1) She must have left the key down stairs, for (2) she said that she would either do that or leave the key in my mailbox. But I know that (3) she didn’t leave it in my mailbox since (4) my mailbox is on the eighth floor, (5) the elevator is broken, and (6) she hates to climb stairs.
Premise indicators: for, since
Conclusion indicators: none
4 + 5 + 6
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19. We know that (1) the cook couldn’t have committed the crime since (2) witnesses saw her stirring the soup at the time of the crime. We also know that (3) the chauffeur couldn’t have done it since (4) a reliable witness claims to have seen him changing a flat tire at the time of the crime. Since we already know that (5) the culprit was the chauffeur, the cook, or the butler, we may conclude that (6) the butler did it.
Premise indicators: since, since, since
Conclusion indicators: we may conclude
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21. We were able to conclude that (1) the rockslide occurred because of an earthquake which took place in the region. First, we know that (2) there was an earthquake in the region because (3) we have found that land masses near the rockslide shifted along a fault line. Second, (4) geologist tell us that no other forces were present at the time which could have led to the rockslide.
Premise indicators: because
Conclusion indicators: we were able to conclude
3
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1
23. (1) You should not complain and worry so much, given that (2) you really have a comparatively good life. (3) Life was much harder for our ancestors for example. (4) A couple centuries ago people didn’t have indoor plumbing; (5) travel was difficult, time consuming and dangerous; (6) general life expectancy was very short, and (7) no one had television.
Premise indicators: given that
Conclusion indicators: none
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24. (1) Death is one of two things: either it is an annihilation in which we have no consciousness at all, or it is a migration of the soul to another place. (2) If there is no consciousness, then death is a great gain. For (3) if the dead are without consciousness, then death is like a sound sleep in which we do not dream, and everyone would agree that (4) such sleep is a happy thing. On the other hand (5) if death is a migration of the soul then we will be able to meet those who have already died. (6) To meet them would be a wonderful experience. We see then that (7) death is not something that we should dread. [Based on Socrates’ speech in Plato’s Apology.]
Premise indicators: for
Conclusion indicators: we see then that
3 + 4
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1 + 2 + 5 + 6
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7
Chapter 2 Personhood Activity
1. Personhood can be defined by having human DNA and the ability to reason ethically. *You* *Your two friends*
2. Personhood can be defined by having complete bodily autonomy and cognitive ability of some kind. *You* *Your two friends* *A relative who is severely mentally impaired* *3-week old fetus* *Chimpanzee* *Embodied strong AI* *4-week old fetus* *Octopus*
3. Personhood can be defined by having advanced neural networks. *Older relative in persistent vegetative state* *A relative who is severely mentally impaired* *3-week old fetus* *Chimpanzee* *4-week old fetus* *Octopus*
4. Personhood can be defined by having human DNA and has or had the ability to reproduce. *You* *Your two friends* *A relative who is severely mentally impaired* *Cancer tumor* *Older relative in persistent vegetative state* *3-week old fetus* *4-week old fetus*
5. Personhood can be defined by the ability to learn and remember information and have some of the genes found in humans. *A relative who is severely mentally impaired* *3-week old fetus* *Chimpanzee* *4-week old fetus* *Octopus*
6. Personhood can be defined by a being that was the result of sexual intercourse between two humans. *Older relative in persistent vegetative state* *A relative who is severely mentally impaired* *3-week old fetus* *4-week old fetus*
7. Personhood can be defined by having human DNA. *Older relative in persistent vegetative state* *Cancer tumor* *A relative who is severely mentally impaired* *3-week old fetus* *4-week old fetus*
8. Personhood can be defined as having some humans genes and an advanced neural network. *Older relative in persistent vegetative state* *A relative who is severely mentally impaired* *3-week old fetus* *Chimpanzee* *4-week old fetus*