Yesterday, you learned about statements, which are sentences that are true or false. Today, you’ll learn what to do with statements: Make arguments!
What Is an Argument?
As mentioned yesterday, logic is the science of reasoning, and the smallest piece of reasoning occurs when we infer a single statement from one or more other statements. Such a piece of reasoning is called an argument, a unit of reasoning in which a single statement is inferred from a set of statements.
Warning: It’s important to realize that an “argument” in logic is not the same as an “argument” in everyday speech. In common usage, an argument is a disagreement between two or more people.
Arguments are the basic unit of logical study, so they will be our main subject for the rest of these lessons. Here are a few important words for talking about arguments:
• Conclusion. The inferred statement is called the conclusion of the argument. In other words, a conclusion is a statement for which evidence is offered or reasons given.
*Warning: Don’t suppose that the conclusion must be the last statement in an argument! The word “conclusion” has other meanings that have to do with the end of something—for instance, an article may have a conclusion at the end, but the conclusion of an argument needn’t come at the end.
• Premise. A premise is a statement offered as evidence or a reason for the conclusion of an argument.
The skill to learn today is how to recognize arguments. Not every set of statements or every written passage is an argument. Statements can be put to other uses, such as descriptions and narration.
How can you tell whether a passage is an argument? One clue is the occurrence of argument indicators, which are words or phrases that indicate that the passage in which they occur contains an argument. Here are a few of the most common argument indicators: therefore, since, so, because, thus, hence.
Warning: With the exception of “therefore,” each of these words has other meanings. For instance, “since” is also used to indicate the passage of time. So, don’t use indicators mechanically — that is, don’t assume that just because you see the word, “since,” you have an argument! Instead, use your background knowledge and understanding of the context in order to determine if the passage is an argument.
Examples: Take a look at the following examples, and using the indicator words, as well as your logical sense, try to determine whether each is an argument or a description.
• “Parents are principally responsible for the education and upbringing of their children and are, therefore, the most qualified persons to select the formal schooling for their children.” (Source: Letter to the Editor)
Whenever you see the word “therefore,” you can be pretty sure that you’re looking at an argument. Here, the letter writer is arguing that parents should select the schooling for their children.
• “The Mississippi receives and carries to the Gulf water from fifty-four subordinate rivers that are navigable by steamboats, and from some hundreds that are navigable by flats and keels. The area of its drainage basin is as great as the combined areas of England, Wales, Scotland, Ireland, France, Spain, Portugal, Germany, Austria, Italy, and Turkey; and almost all this wide region is fertile; the Mississippi valley, proper, is exceptionally so.” (Source: Mark Twain, Life on the Mississippi, Chapter 1)
This passage is just a description rather than an argument. Twain is describing the Mississippi River and its valley, which are the subjects of his book.
• “Since … all bodies, whether upon earth or in the heavens, are heavy … we must certainly allow that gravity is found in all bodies universally.” (Source: Preface to the second edition of Newton’s Principia)
The first word of this excerpt is the argument indicator, “since,” and this is an argument. Newton is arguing that gravity occurs throughout the universe, not just on Earth.
Today, you began learning to recognize arguments and how to tell them from other uses of statements with the help of indicator words. Tomorrow, we’ll start talking about different types of argument indicators.
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