Exam 10: Deduction and Induction: A Closer Look

The following is a weak argument: It has been snowing for sixty days straight, and the prediction is for the snow to continue tomorrow. Thus, tomorrow it will probably be a sunny day.

On deductive arguments. -If the premises and conclusion are all true, then the argument must be valid.

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

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. -No real zombies are conscious … Therefore, no human beings are zombies.

In a generalization from a sample, generally, the larger the sample, the stronger the argument.

The following is a valid argument: The average household in America owns 2.2 cars. The Smiths are an average family. Therefore, they own at least 2.2 cars.

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 creature from the Black Lagoon is angry, then nobody is safe … Therefore, nobody is safe.

More enthymemes. In each case, fill in the missing element (i.e., add a premise or conclusion) so as to turn the enthymeme into a valid deductive argument. -If it rains, then we'll go swimming. It will rain. So ...

Strong or Weak? -Someone stole my textbook. The only person who was eyeing my book when I left class was Joe. Therefore, it is likely that Joe did it.

More enthymemes. In each case, fill in the missing element (i.e., add a premise or conclusion) so as to turn the enthymeme into a valid deductive argument. -All illy pies are reptiles. Therefore, no illy pies are purple.

Assume each of the following is a deductive argument. In each case, is the argument valid or invalid? (V or I) -Ann and Bob won't both be home. Bob will be home. So Ann won't be home.

Strong or Weak? -Professor Jones canceled class three times last quarter. He'll probably cancel class three times this quarter, too.

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. -Every werewolf is hairy. No hairy creatures are reptiles. Therefore, …

More enthymemes. In each case, fill in the missing element (i.e., add a premise or conclusion) so as to turn the enthymeme into a valid deductive argument. -Every time it rains, Joe calls in sick. So Joe will call in sick tomorrow.

Is the argument deductive (D) or inductive (I)? -If Joe cooks, the dinner will be awful. Joe is cooking. The dinner will surely be awful.

On deductive arguments. -Some sound deductive arguments have false premises.

Is the argument deductive (D) or inductive (I)? -If Joe has walking pneumonia, then he is too sick to work. Joe has walking pneumonia. Therefore, he is certainly too sick to work.

Assume each of the following is a deductive argument. In each case, is the argument valid or invalid? (V or I) -Some cars are purple, and some cars are Chevrolets. So some cars are purple Chevrolets.

Is the argument deductive (D) or inductive (I)? -All Ace olives are good to eat. Therefore, these olives, being Ace olives, will surely be good to eat.

Assume each of the following is a deductive argument. In each case, is the argument valid or invalid? (V or I) -All comedians are persons. Jerry is a person. So Jerry must be a comedian.