Exam 10: Deduction and Induction: A Closer Look

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

Is the argument deductive (D) or inductive (I)? -Every time in the past that Jan has spoken, she has gone over her time limit. Therefore, she will probably speak too long tomorrow night at the awards banquet.

Is the argument deductive (D) or inductive (I)? -The meatloaf is gone. The best explanation is that the cat got up onto the table and ate it. Therefore, the cat probably ate it.

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, the creature is not angry.

Some arguments are invalid but sound.

The following is a valid argument: Jim is under sixty. Jan is older than Jim. So Jan must be older than sixty.

The combination you will never find in a weak argument is:

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. -All illy pies are mammals … Therefore, all illy pies are hairy.

Every valid argument has all true premises and a true conclusions.

The following is a strong argument: Joe has eaten lunch at the taco stand every day for sixty days straight. Tomorrow is an ordinary day. Thus, tomorrow he will probably eat there again.

An argument with a false conclusion cannot possibly be a valid argument.

The following is a valid argument: Britney is a good musician. Christa is a good musician. Therefore, they will make a good musical duo.

Is the argument deductive (D) or inductive (I)? -No students at Shoreline are billionaires. Iljoo is a student at Shoreline. Therefore, Iljoo is certainly not a billionaire.

If an inductive argument has all true premises, then you know it is strong.

The following is a valid argument: Jim is over sixty. Jan is not as old as Jim. So Jan must be less than sixty.

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 it rains, then the streets will become wet. If it snows, then the streets will become white. Therefore, either it will not rain, or it will not snow.

In your own words, define the academic subject known as logic. What is it about?

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

Is the argument deductive (D) or inductive (I)? -Portland is 180 miles from Seattle. Therefore, at sixty miles per hour, it must be a three- hour drive.

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. -No frogs are heavy. Only heavy things are large. Therefore, ...