Chapter 3 Basic Logical Concepts

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Chapter 3Basic Logical Concepts
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Deduction vs. Induction

• Deductive Arguments try to prove their
  conclusions with rigorous, inescapable logic.
  Example
• All humans are mortal.
• Socrates is a human.
• Therefore, Socrates is mortal.
• Inductive Arguments try to show that their
  conclusion are plausible (likely or probable),
  given their premises
• So far, every class, the professor has worn a
  tie.
• Therefore, next class, the professor will wear a
  tie.

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• True/False
• Indicate in the space provided whether the
  following statements are true (T) of false (F).
• _____ 1. If an argument contains the indicator
  words probably or likely it is probably an
  inductive argument.
• _____ 2. Deductive arguments always proceed from
  the general to the particular.
• _____ 3. A geometrical proof is an example of an
  inductive argument.
• _____ 4. In a deductive argument the conclusion
  is claimed to follow necessarily from the
  premises.
• _____ 5. No inductive argument provides logically
  conclusive support for its conclusion.

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• _____ 1. If an argument contains the indicator
  words probably or likely it is probably an
  inductive argument.
• _____ 2. Deductive arguments always proceed from
  the general to the particular.
• _____ 3. A geometrical proof is an example of an
  inductive argument.
• _____ 4. In a deductive argument the conclusion
  is claimed to follow necessarily from the
  premises.
• _____ 5. No inductive argument provides logically
  conclusive support for its conclusion.
• 1. T
• 2. F
• 3. F
• 4. T
• 5. T

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• 1. Arguments that try to prove their conclusions
  with rigorous, inescapable logic are
• a. logically reliable.
• b. inductive.
• c. abductive.
• d. deductive.
• 2. An argument in which the conclusion is claimed
  to follow probably from the premises is
• a. implicative.
• b. inductive.
• c. deductive.
• d. none of the above

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• 1. Arguments that try to prove their conclusions
  with rigorous, inescapable logic are
• a. logically reliable.
• b. inductive.
• c. abductive.
• d. deductive.
• 2. An argument in which the conclusion is claimed
  to follow probably from the premises is
• a. implicative.
• b. inductive.
• c. deductive.
• d. none of the above
• 1. d
• 2. b

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• 3. Which of the following is not a common
  induction indicator word or phrase?
• a. it logically follows that
• b. likely
• c. chances are that
• d. none of the above
• 4. If an argument contains the words it must be
  the case that, then it is certain that the
  argument is
• a. inductive.
• b. deductive.
• c. logically reliable.
• d. none of the above

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• 3. Which of the following is not a common
  induction indicator word or phrase?
• a. it logically follows that
• b. likely
• c. chances are that
• d. none of the above
• 4. If an argument contains the words it must be
  the case that, then it is certain that the
  argument is
• a. inductive.
• b. deductive.
• c. logically reliable.
• d. none of the above
• 3. a
• 4. d

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• Distinguishing Deductive Arguments from Inductive
  Arguments
• For each of the following arguments, indicate
  whether it is best interpreted as deductive (D)
  or inductive (I) by circling the appropriate
  letter.
• 1. Most days in the year are weekdays (as opposed
  to weekends). There will come a day when a huge
  asteroid strikes the earth. Thus, the day a huge
  asteroid strikes the earth will likely be a
  weekday. (D/I)
• 2.That Delbert Johnson is not a singer follows
  from the following facts (a) all singers can
  carry a tune, and (b) Delbert Johnson cannot
  carry a tune. (D/I)

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• 1. Most days in the year are weekdays (as opposed
  to weekends). There will come a day when a huge
  asteroid strikes the earth. Thus, the day a huge
  asteroid strikes the earth will likely be a
  weekday. (D/I)
• 2.That Delbert Johnson is not a singer follows
  from the following facts (a) all singers can
  carry a tune, and (b) Delbert Johnson cannot
  carry a tune. (D/I)
• 1. inductive
• 2. deductive

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• 3. So far, no one has ever swum the Atlantic
  Ocean non-stopor even come remotely close to
  doing so. It is unlikely in the extreme,
  therefore, that anyone taking this test will swim
  the Atlantic Ocean non-stop. (D/I)
• 4. Dudley expects to get thirty miles to a gallon
  from the car he bought last week, but thats
  crazy. The car is a 1975 Belchfire with twelve
  cylinders and a 480 horsepower engine, and it
  needs a tune-up. (D/I)

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• 3. So far, no one has ever swum the Atlantic
  Ocean non-stopor even come remotely close to
  doing so. It is unlikely in the extreme,
  therefore, that anyone taking this test will swim
  the Atlantic Ocean non-stop. (D/I)
• 4. Dudley expects to get thirty miles to a gallon
  from the car he bought last week, but thats
  crazy. The car is a 1975 Belchfire with twelve
  cylinders and a 480 horsepower engine, and it
  needs a tune-up. (D/I)
• 3. inductive
• 4. inductive