Reading

Read sections 1.3 and 1.4 in your text.

Instructor's Commentray

After you have completed the exercises for these two sections, you will concentrate on deductive arguments. This focus does not mean that inductive arguments are either uninteresting or unimportant. If you wish to take a closer look at inductive arguments on your own, chapter 9 is devoted exclusively to evaluating inductive arguments. However, you will be responsible for knowing the difference between deductive and inductive arguments and for being able to tell whether a particular argument is deductive or not.

You should make an effort to understand some critical distinctions found in section 1.4. of your text:

true statements/false statements;
valid arguments/invalid arguments; and
sound arguments/unsound arguments.

These distinctions are important in understanding the rest of the course material. Remember that arguments are not true or false; only the statements that make up arguments are true or false. The statements in an argument are the conclusion and the premises. Validity concerns the connection between the premises and the conclusion. In a valid argument the premises could never be true and the conclusion false. “A valid argument is one in which the conclusion must be true if the premises are true.” Soundness should be easy to remember. A sound argument is a valid argument with true premises. Whenever individuals say that they are trying to construct a good deductive argument, they are trying to construct a sound argument.

A point should be made about unsound arguments. They can be unsound for one of three reasons:

The argument could have a false premise.
The argument could be invalid.
The argument could have a false premise and be invalid.

Look carefully at table 1.1 on page 46 of your text. There, Hurley gives you examples of every kind of unsound argument. Note that all of the six different kinds of unsound arguments are unsound for one of the three reasons listed above. The last two arguments in the first column are unsound only because they have at least one false premise. The first two arguments in the second column are unsound only because they are invalid (notice that both arguments contain true premises). The last two arguments of the second column are unsound because they contain a false premise and because they are invalid. It would be wise to study table 1.1 in your text carefully.

Exercises

Do exercise 1.3, pages 40–44, Part I, problems 1, 7, 13, 19, and 25.

Do exercise 1.4, pages 53–57, as follows:

Part I, problems 1, 4, and 7.
Part II, problems 1, 4, and 7.
Part III, problems 1, 7, and 13.