Introductory Logic |
Test #1
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January 6, 2006
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Name: ________________________ |
R. Hammack
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Score: _________
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1. (20 points) Identify each of the following passages as an argument or a non-argument. If the passage is an argument, underline the conclusion.
(a)
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Implied and express claims of product safety refer to the
degree of risk associated with using a product. Since the use of virtually
any product involves some degree of risk, questions of safety are essentially
questions of acceptable known levels of risk.
(M. Velasquez, "The ethiscs of consumer
Production")
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(b)
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Not everything oxygen does is desirable. It causes
iron to rust and copper to corode. It causes food to spoil and it aids in
the decay of wood.
(J.Hill and D. Kolb, Chemestry for Changing
Times)
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(c)
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The period of 16481789 was one of competition among
the primary monarchs of Europe. Wars among the great powers were frequent
but limited. France made major efforts to become paramount, but the balance
of power operated to block French expansion.
(S. Spiegel, World Politics in a New
Era)
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(d)
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A chess problem is mathematics, but it is in some way `trivial'
mathematics
(G. Hardy, A Mathematicians's Apology)
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(e)
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If conditions worsen further so that a massive nuclear first
strike can only be deterred by the bluff or threat of a massive nuclear
retaliation, then it would be morally justified to bluff but not threaten
massive nuclear retaliation.
(J. Sterba, "Just War Theory on Nuclear
Strategy")
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2. (30 points) Each of the following passages is an argument. Underline
the conclusion. Say if the argument is deductive, inductive, valid, invalid,
weak, strong, and (if possible) sound, unsound, cogent, or uncogent.
(a)
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All spiders have wings, because all spiders are birds, and all birds have wings. |
(b)
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Some Americans are blonde. Some Americans are women. Therefore it follows with absolute certainty that some Americans are blonde women. |
(c)
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Almost exactly half of the people in the U.S. are women. Thus, very close to half of the people in Virginia are women. |
(d)
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If you do not attend a class, then you will fail it. If you fail a class, then you will not get credit for it. Therefore, if you do not attend a class, then you will not get credit for it. |
(e)
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Since lots of people have won over $1000 in the Virginia lottery, I will probably win that much if I play the lottery today. |
(f)
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Since most students at Randolph-Macon are billionaires, it's very likely that there are a few billionaires in our Logic class. |
(a)
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All corporations that overcharge their customers are unethical businesses. Some unethical businesses are investor-owned utilities. Thus, some investor-owned utilities are corporations that overcharge their customers. |
Argument Form: All C are U. Some U are I. Thus some I are C |
Subsititution Instance: C = cats U = animals I = dogs |
Resulting Argument: All cats are animals. (T) Some animals are dogs. (T) Thus some dogs are cats. (F) |
Since the argument can be transformed into one with true premises and false
conclusion, it is INVALID.
(b)
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If the government imposes import restrictions, then the price of automobiles will rise. Therefore, the price of automobiles will not rise, since the government will not impose import restrictions. |
Argument Form: If G then P. It is not true that G. Thus it is not true that P. |
Substitution Instance G = "George Washington was hanged" P = "George Washington is dead" |
Resulting Argument: If George Washington was hanged, then George Washington is dead. (T) It is not true that George Washington was hanged. (T) Therefore it is not true that George Washington is dead (F) |
Since the argument can be transformed into one with true premises and false
conclusion, it is INVALID.
(1) Research leading to the development
of the scramjet engine is worthwhile. (2) Commercial aircraft incorporating
such an engine could cross the Pacific in as little as two hours. (3)
This would relieve the fatigue of flights from New York to Tokyo. Also,
(4) such an engine could power future orbiting spacecraft.
(T. Heppenheimer, "A Plane for Space")
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(2) | | | | (3) (4) \ / \ / \ / (1)
5. (14 points) Decide if the following immediate inferences are valid
or invalid. Use either Venn diagrams or the Modern Square of Opposition.
(a)
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No vampires are avid consumers of garlic bread. Therefore, it is false that some vampires are avid consumers of garlic bread. |
The diagram for the premise is:
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The conclusion says it's false that: |
which means there's nothing in the middle, so the conclusion
says
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(b)
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Some country doctors are altruistic healers. Therefore, some country doctors are not altruistic healers. |
The Venn diagrams for the premise and the conclusion are drawn.
Notice these diagrams express different things, so the premise is saying
something the conclusion isn't. Thus the argument is invalid. |
6. (14 points) Use Venn Diagrams to decide if the following arguments are valid or invalid.
(a)
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No A are B. Some C are not B. Therefore, some C are A. |
Here is the Venn diagram for the argument. |
(b)
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All compounds that destroy the ozone layer are environmental
hazards. All chlorofluorocarbons are compounds that destroy the ozone layer. Thus, all chlorofluorocarbons are environmental hazards. |
The argument form is |