Logic and Structure

Evaluate use of logic and structure in texts

In previous writing classes you’ve taken, you’ve likely encountered certain patterns to help you construct essays, like the 5-paragraph essay or the 3-point thesis statement. You may have also noticed that very few things you read, either for class or in the “real world,” follow these formulas themselves. Those patterns serve as good scaffolds for learning to write, but more accomplished (and more widely-read) authors tend to move beyond these simple patterns.

That said, they still use some kind of pattern to help them write, and to help their audiences anticipate what will come next. As an active reader, you will need to first identify these patterns, and then evaluate how well these patterns fit with the purpose of the text. You have the power to critique how well-suited, or not, the author’s pattern matches with his purpose.

If focus is the foundation for constructing a piece of writing, organization is the the structural framework for that writing. Organization is important to effective writing because it provides readers with a framework to help them fulfill their expectations for the text. A well-organized piece of writing supports readers by making it easy for them to follow, while a poorly organized piece leads readers through a maze of confusion and confounded or unmet expectations.

Organization, simply put, is the logical progression and completeness of ideas in a text.

In this section, we’ll look at logic as a science of reasoning that aids writers in being creative in the generation of ideas. What follows is a discussion of some of the uses of logic that writers employ in creating persuasive or argumentative essays.

A sound, well-reasoned, and compelling text is one of the most effective and persuasive communicative acts that human beings ever create.

Two Ways of Understanding

We have two basic approaches for how we come to believe something is true.

The first way is that we are exposed to several different examples of a situation, and from those examples, we conclude a general truth. For instance, you visit your local grocery store daily to pick up necessary items. You notice that on Friday, two weeks ago, all the clerks in the store were wearing football jerseys. Again, last Friday, the clerks wore their football jerseys. Today, also a Friday, they’re wearing them again. From just these observations, you can conclude that on all Fridays, these supermarket employees will wear football jerseys to support their local team.

This type of pattern recognition, leading to a conclusion, is known as inductive reasoning.

Knowledge can also move the opposite direction. Say that you read in the news about a tradition in a local grocery store, where employees wore football jerseys on Fridays to support the home team. This time, you’re starting from the overall rule, and you would expect individual evidence to support this rule. Each time you visited the store on a Friday, you would expect the employees to wear jerseys.

Such a case, of starting with the overall statement and then identifying examples that support it, is known as deductive reasoning.

The Power of Inductive Reasoning

You have been employing inductive reasoning for a very long time. Inductive reasoning is based on your ability to recognize meaningful patterns and connections. By taking into account both examples and your understanding of how the world works, induction allows you to conclude that something is likely to be true. By using induction, you move from specific data to a generalization that tries to capture what the data “mean.”

Imagine that you ate a dish of strawberries and soon afterward your lips swelled. Now imagine that a few weeks later you ate strawberries and soon afterwards your lips again became swollen. The following month, you ate yet another dish of strawberries, and you had the same reaction as formerly. You are aware that swollen lips can be a sign of an allergy to strawberries. Using induction, you conclude that, more likely than not, you are allergic to strawberries.

Data: After I ate strawberries, my lips swelled (1st time).

Data: After I ate strawberries, my lips swelled (2nd time).

Data: After I ate strawberries, my lips swelled (3rd time).

Additional Information: Swollen lips after eating strawberries may be a sign of an allergy.

Conclusion: Likely I am allergic to strawberries.

The results of inductive thinking can be skewed if relevant data are overlooked. In the previous example, inductive reasoning was used to conclude that I am likely allergic to strawberries after suffering multiple instances of my lips swelling. Would I be as confident in my conclusion if I were eating strawberry shortcake on each of those occasions? Is it reasonable to assume that the allergic reaction might be due to another ingredient besides strawberries?

This example illustrates that inductive reasoning must be used with care. When evaluating an inductive argument, consider

• the amount of the data,
• the quality of the data,
• the existence of additional data,
• the relevance of necessary additional information, and
• the existence of additional possible explanations.

Inductive Reasoning Put to Work

A synopsis of the features, benefits, and drawbacks of inductive reasoning can be found in this video.

https://youtube.com/watch?v=wzEOwleZNnA%3Ffeature%3Doembed%26rel%3D0

The Power of Deductive Reasoning

Deductive reasoning is built on two statements whose logical relationship should lead to a third statement that is an unquestionably correct conclusion, as in the following example.

All raccoons are omnivores.
This animal is a raccoon.
This animal is an omnivore.

If the first statement is true (All raccoons are omnivores) and the second statement is true (This animal is a raccoon), then the conclusion (This animal is an omnivore) is unavoidable. If a group must have a certain quality, and an individual is a member of that group, then the individual must have that quality.

Going back to the example from the opening of this page, we could frame it this way:

Grocery store employees wear football jerseys on Fridays.
Today is Friday.
Grocery store employees will be wearing football jerseys today.

Unlike inductive reasoning, deductive reasoning allows for certainty as long as certain rules are followed.

Evaluating the Truth of a Premise

A formal argument may be set up so that, on its face, it looks logical. However, no matter how well-constructed the argument is, the additional information required must be true. Otherwise any inferences based on that additional information will be invalid.

Inductive reasoning can often be hidden inside a deductive argument. That is, a generalization reached through inductive reasoning can be turned around and used as a starting “truth” for a deductive argument. For instance,

Most Labrador retrievers are friendly.
Kimber is a Labrador retriever.
Therefore, Kimber is friendly.

In this case we cannot know for certain that Kimber is a friendly Labrador retriever. The structure of the argument may look logical, but it is based on observations and generalizations rather than indisputable facts.

Methods to Evaluate the Truth of a Premise

One way to test the accuracy of a premise is to apply the same questions asked of inductive arguments. As a recap, you should consider

• the amount of the data,
• the quality of the data,
• the existence of additional data,
• the relevance of the additional data, and
• the existence of additional possible explanations.

Determine whether the starting claim is based upon a sample that is both representative and sufficiently large, and ask yourself whether all relevant factors have been taken into account in the analysis of data that leads to a generalization.

Another way to evaluate a premise is to determine whether its source is credible.

• Are the authors identified?
• What is their background?
• Was the claim something you found on an undocumented website?
• Did you find it in a popular publication or a scholarly one?
• How complete, how recent, and how relevant were the studies or statistics discussed in the source?

Overview and Recap

A synopsis of the features, benefits, and drawbacks of deductive reasoning can be found in this video.

https://youtube.com/watch?v=oBnKgxcdSyM%3Ffeature%3Doembed%26rel%3D0

Evaluate Unstated or Suppressed Premises As Well As Stated Ones

An unstated or suppressed premise is assumed rather than voiced outright, but is nevertheless needed for an argument to work. Consider this highly unscientific poll conducted by a TV news station. “Which do you believe Senator Hillary Clinton is most out of touch with: illegal immigration, border security, or the American people?” The pollster is operating as if it is unquestionable that Clinton is out of touch with something. In other words, the question presupposes that she is “out of touch.” However, this unstated premise is debatable once it is brought out into the open. Is she in fact out of touch at all?

A listener or reader who is not alert to such unstated or suppressed premises is, without realizing it, agreeing to debate on the communicator’s terms—when those terms may be unfair. In fact, on more complex or serious issues it is often things people take for granted that may actually deserve the most critical scrutiny. For example, in the argument “This medication is labelled as totally natural, so it is safe for me to take it,” the suppressed premise—that “natural” guarantees “safe”—is not trivial and can certainly be challenged.

Argument Diagramming

Besides recognizing the use of induction and deduction, you can use diagramming or outlining to develop an understanding of an argument’s overall structure. Remember that an argument as defined here isn’t a “quarrel,” but rather a group of statements, some of which, the premises, are offered in support for another, the conclusion. So the first order of business in analyzing an argument is to recognize what the main claim is—the conclusion—and what other claims are being used to support it—the premises. This is much easier to do when the author is explicit about the steps in the argument, where premise and conclusion “indicator” terms appear in the text as signposts.

When you are diagramming or outlining an argument, if the “flow” of an argument from premises to conclusion isn’t readily apparent, then remember to use the above indicator terms to help you decide which claim is the conclusion and which claims are the premises. Using the indicator terms is particularly helpful because a conclusion may be stated first, last, or anywhere in between. People do all three when they write or talk in real life, so we cannot tell whether a statement is a conclusion simply by where it is positioned in the argument.

The Purpose Behind Diagramming an Argument

Diagramming or mapping someone else’s argument serves a double purpose. First, the process helps you clearly see just what the other person is saying. It helps you identify the logical structure of the argument, which is necessary if you are to assess the strengths and weaknesses of the argument in order to know whether or not to accept it. Second, you develop skills of analysis that you will need in order to organize and present arguments in support of a position that you may want to take on some question or issue.

Steps in Diagramming an Argument

Here are the basic moves that are required in order to create a clear diagram or outline of an argument.

1. Identify all the claims made by the author. Since a sentence can contain multiple claims, rewrite statements so that you have one claim per sentence. Adopt some sort of numbering or labeling system for the claims.
2. Eliminate “fluff.” Ignore repetitions, assurances (assertions not backed by evidence or reasons), and information that is unrelated to the argument.
3. Identify which statements are premises and which statement is the main conclusion.
4. Recognize that there may be sub-conclusions in addition to a final or main conclusion. You may think of a sub-conclusion as the end point of a sub-argument nested inside the larger argument. Although the sub-conclusion is itself the conclusion of a nested argument, supported by premises, it also functions as a premise supporting the final or main conclusion.
5. Recognize that some premises are independent and others linked. If you were drawing or mapping the argument, you would be able to draw an arrow from an independent premise directly to the conclusion it supports. Linked premises, however, are multiple statements that must be combined to provide support for a conclusion. If you were drawing or mapping the argument, you would have to find some way to show that the linked premises as a group support the conclusion. You might use color coding, or underlining, or circling, or + signs—some way to connect the linked premises before drawing one arrow from the clustered premises to the conclusion they support.

Using the Argument’s Paragraphing to Evaluate the Premises

An author must organize her material to guide the audience through her argument. One tool available to an author is the paragraph. The sentences clustered together in a paragraph should be tightly connected in terms of content. In the most common form of paragraph, the clustered sentences collectively develop an idea explicitly stated in a topic sentence. The paragraphs themselves should be placed in an order that reflects some overall plan so that the paragraphs reveal the steps or stages of the argument.

The premises may be said to be key steps or stages in the argument. A well-constructed argument therefore may use each premise as a topic sentence for a paragraph. Additionally, a premise may serve as the guiding idea for a group of paragraphs, each developing a subtopic. For example, the premise, reached by induction, that “College students overestimate the amount of binge drinking that is taking place” might introduce a cluster of three paragraphs, each showing that the overestimation varies by subgroup—with member of sororities, member of fraternities, and non-Greek populations arriving at different estimates.

Look to see whether the author has used paragraphing-by-premise to organize her argument and outline its structure for the audience. You should also ask yourself whether any paragraphs are missing. That is, as you consider what premises serve as the foundations of the argument, be alert for the suppressed ones, the premises that the author presupposes. These unacknowledged premises may be ones that the author hopes the audience will not notice or question. In your analysis call her on it by determining where a paragraph on that premise should have appeared in the argument.

The Similarity Between Conclusions and Thesis Statements

When we talk about a paper, we usually talk about the paper’s main claim as being its thesis statement. But of course a paper that just makes a claim or states an opinion but offers no supporting reasons or arguments isn’t much of a paper. We would be bothered by reading an editorial in which someone stated a strong opinion on some public issue yet did nothing to justify that opinion.

When an author supports a thesis with reasons, then the thesis statement can be described as the conclusion of an argument, with the supporting reasons being that argument’s premises. The argument now has a structure that can be outlined or diagrammed.