Logic

III. We have spoken earlier of the relation between or among propositions. What is a proposition or statement (we will use these words interchangeably)?

A. Statement: a verbal expression that can be regarded as true or false (but not both). Hence, a statement or a proposition is a sentence with a truth-value. We can still regard a sentence as a statement even if the truth-value of the statement is not known.

B. Hence logic is just concerned with those statements that have truth-values. (There is very much of life that is irrelevant to logic.)

Consider the confusion that would result if we considered the following sentences as statements:

1. "Good morning." (What's so good about it?)

2. "You are looking good today." (Well, I just saw my doctor and ...)

3. "What is so rare as a day in June? Then, if ever, come perfect days..." (Well, I don't know about that.)

4. To a waiter: "I'd like a cup of coffee." (Yeah, but I think bigger, I'd like a BMW.)

Thus, phatic communication, greetings, commands, requests, and poetry, among other uses of language, are not mean to be taken as statements.

C. Which of the following sentences are statements?

1. There is iron ore on the other side of Pluto.

2. Tomorrow, it will rain.

3. Open the door, please.

4. Whales are reptiles.

5. "Yond' Cassius has a lean and hungry look."

6. Pegasus has wings.

7. You should vote in all important elections.

IV. More distinctions with regard to statements are worth suggesting.

A. Consider whether there are two statements in the box:

A Republican is President (of the U.S.).

A Republican is President (of the U.S.).

1. Aside from the ambiguity of when the statements are uttered,