Exam 10: Deduction and Induction: A Closer Look

The following is a valid argument: Jim is at least sixty. Jan is younger than Jim. So Jan must be younger than sixty.

On deductive arguments. -If a deductive argument has all false premises, then it must be invalid.

Aristotle studied under Plato.

If an argument has premises that are probably true, then the argument must be inductive.

The following is a strong argument: For fifty years it has rained every day of the year in Dallas, Texas. Thus, tomorrow it will rain in Dallas, Texas.

Assume each of the following is a deductive argument. In each case, is the argument valid or invalid? (V or I) -No aardvarks are reptiles. No reptiles are warm-blooded. So all aardvarks are warm-blooded.

Think with Socrates does not contain a section on enthymemes. However, the concept can be defined briefly. This exercise defines an enthymeme and gives students a chance to practice filling in holes in incomplete deductive arguments. An enthymeme is an argument that is missing one or more premises or a conclusion. Each of the following deductive arguments is missing either a premise or a conclusion. (Thus, each is an enthymeme.) Add a statement to each so as to turn the enthymeme into a valid argument. -Some bats are pets. Therefore, some pets are scary-looking creatures.

On critically evaluating inductive arguments. Read the following arguments and carry out the instructions below. -Consider this argument: I've met four long-haul truckers, and all four were polite and well-mannered individuals. Therefore, the next one I meet will probably also be polite and well-mannered. In each of the following cases, would the addition make the argument stronger or weaker? Or would it leave things unaffected? a. All four listened exclusively to country music. b. One was of Italian descent, one was of Polish descent, one was of Ethiopian descent, and one was of Japanese descent. c. One of the four was from L.A., one was from New York, one was from Seattle, and one was from Alabama. d. All four were from Seattle. e. All four were in their thirties. f. One was still in his teens, one was in his twenties, one was in his thirties, and one was over forty. g. I've actually met eight, and all were polite and well-mannered. h. I met an additional long-haul trucker, and he was polite. i. I met an additional long-haul trucker, and he was well-mannered. j. I met an additional long-haul trucker, and he was rude and crude. k. I change the conclusion to: All long-haul truckers are polite and well-mannered.

Think with Socrates does not contain a section on enthymemes. However, the concept can be defined briefly. This exercise defines an enthymeme and gives students a chance to practice filling in holes in incomplete deductive arguments. An enthymeme is an argument that is missing one or more premises or a conclusion. Each of the following deductive arguments is missing either a premise or a conclusion. (Thus, each is an enthymeme.) Add a statement to each so as to turn the enthymeme into a valid argument. -If the werewolves are on the loose again, then London is not safe at night. London is safe tonight. So …

If an argument is strong, then it must have a true conclusion.

On deductive arguments. -If an argument is deductively sound, then it has true premises.

As an academic subject, logic is the study of...

The following argument is invalid: All students are allergic to tuna. Jim is a student. Therefore, Jim must be allergic to tuna.

On deductive arguments. -If an argument is valid, then its conclusion is likely but not certainly true.

All arguments with true conclusions are valid arguments.

A generalization from a sample is deductive in nature.

The following argument is valid: All students are billionaires. All Republicans are billionaires. So all students are Republicans.

An analogy is a similarity between two things.

The text divides all arguments into these very general categories:

Strong or Weak? -Over the past month, Fred has eaten eight burritos at Gorditos. All eight were good. For his next dinner, he plans to buy another Gordito burrito. His next burrito will likely be good.