Writing for the College-Bound

Unit 7: Supporting Your Claim

Two Broad Classes of Appeal and Argument

In the original Star Trek TV series, the three main characters formed a single dramatic entity: Spock provided the rational insight presumably based on unbiased logic (though it was seldom in fact so simple), Dr. McCoy provided the “human” aspect or emotional insight, and Captain Kirk resolved the two approaches into a single action that would solve the problem.

As humans we are susceptible to both appeals to reason and appeals to emotion. We have to balance these two kinds of appeal to make a coherent and complete argument. In this unit, we look at ways of constructing and supporting a rational or logical argument, which is an appeal to the intellect. In the next unit, we’ll take a brief survey of the most common logical fallacies and look the improper use of certain kinds of emotional appeals. In the final unit of our close look at the persuasive argument, we’ll talk about forestalling counter-arguments.

Using examples or precedents

Citing concrete evidence is the best way to support your claim. If you can show actual examples, you can allow the reader to see how you arrived at your position from your own observations and experience. The example must be directly related to the claim, and the standards for evaluation, as we discussed last time, should be clear. In this context, the word “concrete” refers to evidence that is substantial, demonstrable, and specific.

Claim: One way in which the Mac OS shows its superiority is the ease with which software can be installed on a Macintosh.

Example: Many multimedia CDs work on both Macintoshes and Windows platforms. For example, to install “The Way Things Work” on the Macintosh, you insert the disk and drag the program icon to the desktop. To install the same program on a Windows NT machine, you must find Setup.exe on the disk, and run a special installer program.

Citing a precedent is referring to a previous similar situation. This is especially useful if you know that your audience is acquainted with the previous situation. You are more likely to convince a teacher to grant you an extension on late homework if you know that he or she has just done so for another student in circumstances similar to yours.

Cause and effect

Another important form of argument is to show how some event or result is related to its causes. This is particularly important if you are arguing that the effects need to be changed. Unless you correctly identify and establish the causes of those effects, you cannot propose a valid program of re-evaluation or change. Sometimes establishing this relationship is itself the point of the essay!

Undesirable effect:: People who smoke cigarettes have a higher incidence of lung cancer than those who do not smoke cigarettes.

Cause: Tobacco use significantly increases one’s chances of contracting cancer of the lungs, throat, or tongue. [The problem here is that scientific research can only prove a statistical likelihood for the connection, not an absolute cause in each particular case].

Two forms of reasoning relate causes and effects — deductive and inductive reasoning. In the most general terms, deductive reasoning is reasoning from general principles, while inductive reasoning is reasoning to general principles. While in most real-world situations one is called upon to use both kinds of reasoning, they are functionally distinct.

Deductive reasoning

In deductive reasoning, we go from a cause to an inevitable affect. The logic for deductive reasoning is basically "if....then" logic: of the cause exists, the effect must follow. This kind of reasoning is good when you have a very clear relationship between cause and effect, but also has other implications.

When you cannot cite a direct example, you may have to draw an abstract conclusion. Deductive reasoning involves taking a general principle (the major premise) and applying it to a specific instance (the minor premise), then drawing a conclusion about the specific instance. The classic example of deductive reasoning is the syllogism:

Major Premise: All men are mortal.

Minor Premise: Socrates is a man.

Conclusion: Socrates is mortal.

The advantage of this type of reasoning is that if the major and minor premises are both true, the conclusion must be true. However, the syllogism form doesn’t lend itself well to most essays.

One way of using this type of reasoning in an essay is to draw on the audience’s knowledge and experience to supply the major premise. The claim:

Our students have too much homework and their assignments this week need to be shorter.

draws on the (possibly true but probably arguable) assumption that students have a limited capacity for schoolwork. You could restate this in syllogistic form:

Major Premise: Students can only do so much work a week.

Minor Premise: My students must do more work than that.

Conclusion: My students are over-burdened.

Notice, however, that if either the major or the minor premise is false in even one case, the conclusion will be unreliable. One of the more common mistakes in essay writing to assume too great a generality:

John is a Mac user, so what does he know about computers?

assumes, perhaps erroneously, that all Mac users are computer-illiterate.

Inductive reasoning

Inductive reasoning is in a sense the reverse of deductive reasoning: you make a general statement based on specific examples. Here you have the effects; the problem is establishing which of several possible causes is the appropriate one. Usually, it is much harder to prove a direct link from an effect to a cause by inductive reasoning than it is to prove the link between cause and effect by deductive reasoning, but often, you only have effects and cannot use deductive methods. Science is, for the most part, an inductive process. This is why the conclusions of science are never logically absolute, but can be maintained only until a single contradictory case comes along to disprove them.

Many essays involve this kind of reasoning, particularly essays of definition.

Claim: The internet is a useful source of information.

Substantiation by example: I used the internet last week to find out the side effects of my new medication, the latest news on the stock market, and to locate a copy of a book published in 1651.

Notice that inductive reasoning can’t prove that every case will result in useful information; I haven’t been able to find out certain information via web surfing, and I have run across websites that contain information that I definitely consider not useful.

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