Chapter 3 Basic Logical Concepts

Deduction vs. Induction Deductive Arguments try to prove their conclusions with rigorous, inescapable logic. Example: 1.All humans are mortal. 2.Socrates is a human. 3.Therefore, Socrates is mortal. Inductive Arguments try to show that their conclusion are plausible (likely or probable), given their premises: 1.So far, every class, the professor has worn a tie. 2.Therefore, next class, the professor will wear a tie.

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.

_____ 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

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. 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

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. 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

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)

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

3. So far, no one has ever swum the Atlantic Ocean non-stop—or 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 that’s crazy. The car is a 1975 Belchfire with twelve cylinders and a 480 horsepower engine, and it needs a tune- up. (D/I)

3. So far, no one has ever swum the Atlantic Ocean non-stop—or 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 that’s 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