Logic Handout

 Logic & Language ^{a primer[1]}

 

Basic Ideas

The basic unit of language is the proposition. A proposition is a statement (not a sentence) that can be judged true or false.

“It is raining” either truly or falsely reports a state of affairs. We must agree that propositions can be judged                as such if we want to “mean what we say.”

In a basic analysis of human communication, there are three ways that we use language:

·         We use language informatively. We demand that propositions tell us things about the world. The statement, “Your instructor is under thirty years of age” (whether true or false) tells you something about your instructor. When we are making an argument, we use language in this way.

·         We use language emotively. Don’t get this confused with the technical use in your text. This kind of language communicates feelings, emotions, or attitudes. The statement, “I am sad” tells us only that I am sad, not why (which would require an informative statement) I am sad.

·         We use language directively when we try to create or prevent an action. Commands (Open the door!) and requests (please open the door.) are the best examples of directive language.

As Copi and Cohen remind us, “effective communication demands certain combinations of [these] functions…Now, wants and desires are special kinds of what we have been calling ‘attitudes’ and ‘feelings,’ and beliefs are commonly influenced by the information received. Consequently, we sometimes succeed in causing others to act by evoking in them the appropriate attitudes, and sometimes by giving them information that affects their relevant beliefs.” (75)

Emotively Neutral Language

A good trick for successful arguments is to play down emotive language. “When we are trying to learn what really is the case, or trying to follow an argument, distractions will be frustrating—and emotion is a powerful distraction” (96). At times, emotive language brings with it unnecessary or inappropriate baggage. Learning to use emotively neutral (or unbiased) language will make your argument more convincing to the reader or hearer.

Laws of Logic Necessary for Communication

Don’t be intimidated! We rely on these laws every day to make sure that people are telling the truth, and that we can trust what they say (remember the case study in Rachels, ch. 2)! Take the example of a bachelor. By definition, we agree that a bachelor is the same as an unmarried male.

·         The law of identity says that if any statement is true, then it is true. This is called a tautology. If it is true that a bachelor is an unmarried male, then it is true. If we question this basic idea, then we begin (what is called in the jargon of philosophy) a reductio ad absurdum.

·         The law of non-contradiction says that it cannot be true that a bachelor is an unmarried male and false that a bachelor is an unmarried male in the same sense at the same time. Otherwise, how would we know how to identify a “bachelor?”

·         The law of excluded middle says that every proposition is either true or false. It is either true that bachelors are unmarried males or it is false that bachelors are unmarried males. A bachelor cannot be both married and single.

With these tools, it will be easy for you to recognize both true and faulty statements! Don’t overlook or underestimate their importance.

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[1] See Irving Copi and Carl Cohen. Introduction to Logic, 11^th Ed. New Jersey: Prentice Hall, 2001.