Logic and Structure


Learning Objectives

  • identify patterns of logical organization in texts
  • identify basic features of rhetorical patterns (narrative, comparison, definition, etc.)
  • identify logical structures in argument
  • identify logical fallacies

Photo of stone path pavers. Most of them are laid out orderly, but a central cluster are in disarray, with several missing.Human beings love order, and we will try to impose order in almost every situation.  That includes reading.  Clearly, most reading relies on understanding words in the order they appear in a sentence.  Even beyond that, we anticipate patterns and shapes that particular types of writing will take, and we build expectations based on the first few sentences that we read.

This section will help you understand what you can learn from a piece of reading based on the shape it takes, in addition to what the words themselves convey.

Rhetorical Modes

We’ve been focusing on broad categories of reading materials so far: literature, journalism, textbooks, and academic writing. Since most of the reading (and writing!) you’ll do throughout your college career falls into the “academic writing” category, this is a good point to slow down and examine the building blocks of academic writing more closely.

Rhetoric is the study of writing, so the basic types of academic writing are referred to as rhetorical modes. Let’s look at 10 of the most common types.

1. Narration

The purpose of narration is to tell a story or relate an event. Narration is an especially useful tool for sequencing or putting details and information into some kind of logical order, usually chronological.

Literature uses narration heavily, but it also can be useful in academic writing for strong impact.

An academic essay about the impact of lead in the drinking water in Flint, Michigan, for instance, might include a narrative section that tells the story of one particular family that’s been impacted. This will help illustrate the broader impacts on the community.

2. Description

The purpose of description is to re-create, invent, or visually present a person, place, event, or action so that the reader can picture that which is being described. It is heavily based on sensory details: what we experience through our five senses.

Description is very useful in writing of all types.

In our essay about lead in drinking water, sensory details such as the color of the lead-contaminated water coming out of the tap, or the taste of it when used for cooking, will be informative and help clarify the dangers to the community of Flint. 

3. Example

We’ve been looking at examples so far, with the lead in the water of Flint, Michigan. An exemplification essay extends this idea even further: it carries one or more examples into great detail, in order to show the details of a complex problem in a way that’s easy for readers to understand.

Writing in detail about the drinking water crisis in Flint might be used to exemplify the political situation where a state governor appoints an emergency manager over a city, taking authority away from a mayor or a town council. On the surface, it seems like these two ideas aren’t connected, so the extended example of the drinking water situation will help readers to understand the potential consequences of removing local leadership.

4. Definition

In the vocabulary section we talked about word definitions in great detail. A definition essay takes the concept of “definition” more broadly, moving beyond a dictionary definition to examine a word or concept as we actually use and understand it.

If we use the term “drinking water crisis” to apply to the situation in Flint, Michigan, what does that actually mean? At what point does the term “crisis” apply? A definition essay would examine the various factors that shape a public crisis, such as the level of lead contamination in water determined to be dangerous, the costs of drinking water to citizens, the difficulty in accessing water in other ways, and the damage lead exposure can have to children.

5. Process Analysis

Analyzing a process can also be thought of as a “how-to” essay. Technical writing includes a lot of process analysis, for instance. Academic writing can incorporate process analysis to show how an existing problem came to be, or how it might be solved, by following a clear series of steps.

Tracing the steps that led to the current drinking water problems in Flint would prove a useful exercise in a process analysis essay. Showing exactly what steps were taken, and in what order, would help illustrate for readers how similar situations could be avoided in other communities in the future.

6. Division/Classification

A classification essay takes one large concept, and divides it into individual pieces. A nice result from this type of writing is that it helps the reader to understand a complex topic by focusing on its smaller parts. This is particularly useful when an author has a unique way of dividing up the concepts, to provide new insight into the ways it might be viewed.

Part of the reason that the Flint drinking water issue has gotten so much attention, is that it’s such a thorny issue with so many potential long-term effects. A classification approach to this topic could divide the overall concept of “crisis” into individual threads: the political implications, the public health implications, the financial implications, and the educational implications.

7. Comparison/Contrast

Comparison focuses on similarities between things, and contrast focuses on their differences. We innately make comparisons all the time, and they appear in many kinds of writings. The goal of comparison and contrast in academic essays is generally to show that one item is superior to another, based on a set of evaluations included as part of the writing.

A path to deeper understanding of the Flint drinking water crisis would be to look at another community that has experienced something similar. Comparisons and contrasts might be made in how the situation arose in each location, how it was handled by public officials and private citizens, and how it was ultimately resolved.

8. Cause/Effect

If narration offers a sequence of events, cause/effect essays offer an explanation about why that sequence matters. Cause/effect writing is particularly powerful when the author can provide a cause/effect relationship that the reader wasn’t expecting, and as a result see the situation in a new light.

We recognize that lead contamination in drinking water is a problem, but many readers may not know exactly why that is. Drawing a cause/effect relationship between lead exposure in childhood, and later learning disabilities and physical problems once these children grow up, would be helpful for understanding the long-term impacts possible from the current situation in Flint.

9. Problem/Solution

This type of academic writing has two equally important tasks: clearly identifying a problem, and then providing a logical, practical solution for that problem. Establishing that a particular situation IS a problem can sometimes be a challenge–many readers might assume that a given situation is “just the way it is,” for instance.

If the fact that the drinking water supply in Flint contains lead is the problem, then an academic problem/solution essay will establish WHY it’s a problem. This might include noting the EPA guidelines for lead in the water supply, and what Flint’s water testing results reveal. Then, this essay would need to establish a solution for the situation that would be both practical and feasible. The temporary solution many residents are using currently is to buy bottled water to drink, cook, and bathe with. A problem/solution essay on this subject will need to offer a more manageable long-term solution for these residents.

10. Argument & Persuasion

The purpose of argumentation (also called persuasive writing) is to prove the validity of a point of view, by presenting sound reasoning to thoroughly convince the reader. These assume that the reader is initially uninformed about the topic, or holds a viewpoint that differs from the author’s. The author’s goal is to bring the reader around to his or her way of thinking on the matter.

Many different people, organizations, and political groups have been blamed along the way for the water crisis in Flint. A persuasive paper looking at who’s ultimately responsible would offer a definitive answer for which group or person deserves the bulk of the blame. It would also effectively address why this matters to the reader–why a reader should care about making sure that the guilty party is ultimately held responsible for their actions.

As the examples of the Flint, Michigan drinking water situation show, there is a lot of overlap between the different rhetorical modes. Many academic essays combine two or more different rhetorical modes in one finished product. This leads to a rich reading experience.

Logical Arguments

Anything you read that includes an attempt to persuade you to think a certain way is likely to include logical argument as part of that persuasion.

The text below introduces the idea of premises and conclusions. As you view this, think about the relationship of premises and conclusions as they align with main ideas and supporting evidence in paragraphs that we explored earlier in this module.

Elements of an Argument

Argumentation Vocabulary

Claim: a statement or opinion that is either true or false

Argument: a claim supported by premises

Conclusion: the main claim in an argument

Premises: claims that support and argument’s conclusion

A claim is an assertion about the truth, existence, or value of something that is either true or false. Claims are also called statements or propositions.

When supported by premises, a claim becomes a conclusion. For example:

  • This class is easy.
  • The Detroit Lions have the potential to make the NFL playoffs.
  • This chemical structure is unstable.
  • Democratic socialism is superior to a pure democracy.

An argument is an assertion that contains both a conclusion and premises. It is a statement of fact or opinion that is based on evidence. Keep in mind that not all statements are arguments, and some statements may contain multiple arguments.

Test It Out

Which of the following statements is an argument?

  1. Vending machines stocked with soda or candy should be removed from all public schools.
  2. Star Wars is the best movie ever.
  3. We’d better leave now. If we don’t, we might miss the last train and we’ll be stuck here all night.

A conclusion is the main claim of an argument that is supported by a premise. It is the logical result of the relationship between the premises. Identifying the conclusion is the first step in understanding the argument.

But how do you identify the conclusion? Follow these steps:

  1. Ask, “Is the statement the main point, or is it a claim given to support another statement in the argument?
  2. Identify the indicator word that often precedes the conclusion, such as
Therefore Thus As a result That’s why Consequently So
This Means This shows It follows that This suggests Hence Accordingly

Test It Out

What is the conclusion in each of the following arguments?

  1. Abortion is wrong because all human life is sacred.
  2. It’s flu season and you work with kids, so you should get a flu shot.
  3. We should believe that rocks exist because we are able to see them.
  4. John will probably receive the next promotion since he’s been here the longest.
  5. We must reduce the amount of money we spend on space exploration. Right now, the enemy is launching massive military buildup, and we need additional money to purchase military equipment to help match the anticipated increase in the enemy’s strength.
  6. It’s a beautiful day. We should go to the park. Besides, I need some exercise.
  7. That movie has had horrible reviews. My sister saw it and said it was boring and her friend spotted three mistakes. Pick a different movie. I am sure we can find something better.

A premise is a reason offered as support, or evidence, for another claim. It is often indicated by these words:

Because For As
Since Inasmuch as As shown by
Given that As indicated by The reason is that

Consider the following statement: Today’s freshmen cannot write very well. Joe is a freshman, so he must be a poor writer. The premises and conclusion are identified as follows:

Premise Today’s freshmen cannot write very well
Premise Joe is a freshman,
Conclusion so he must be a poor writer.

Practice identifying the premises and conclusions

In order to identify the premises and conclusion, you should first rewrite the argument in standard form. You do this by identifying which claim is the conclusion, then working backwards to identify which claims are premises that support the conclusion. It should look like this:

Standard Form
Premise 1:
Premise 2:

Practice in the following presentation:

Deductive and Inductive Arguments


In the process of deduction, you begin with some statements, called “premises,” that are assumed to be true, you then determine what else would have to be true if the premises are true.

For example, you can begin by assuming that God exists, and is good, and then determine what would logically follow from such an assumption. You can begin by assuming that if you think, then you must exist, and work from there.

With deduction you can provide absolute proof of your conclusions, given that your premises are correct. The premises themselves, however, remain unproven and unprovable.[1]

Examples of deductive logic:

  • All men are mortal. Joe is a man. Therefore Joe is mortal. If the first two statements are true, then the conclusion must be true.[2]
  • Bachelors are unmarried men. Bill is unmarried. Therefore, Bill is a bachelor.[3]
  • To get a Bachelor’s degree at Utah Sate University, a student must have 120 credits. Sally has more than 130 credits. Therefore, Sally has a bachelor’s degree.

Two rectangles. Left: General Principle. Right: Special Case. An arrow pointing left to right above them is labeled "deductive reasoning." An arrow pointing right to left below them is labeled "inductive reasoning."Induction

In the process of induction, you begin with some data, and then determine what general conclusion(s) can logically be derived from those data. In other words, you determine what theory or theories could explain the data.

For example, you note that the probability of becoming schizophrenic is greatly increased if at least one parent is schizophrenic, and from that you conclude that schizophrenia may be inherited. That is certainly a reasonable hypothesis given the data.

However, induction does not prove that the theory is correct. There are often alternative theories that are also supported by the data. For example, the behavior of the schizophrenic parent may cause the child to be schizophrenic, not the genes.

What is important in induction is that the theory does indeed offer a logical explanation of the data. To conclude that the parents have no effect on the schizophrenia of the children is not supportable given the data, and would not be a logical conclusion.[4]

Examples of inductive logic:

  • This cat is black. That cat is black. A third cat is black. Therefore all cats are are black.[5]
  • This marble from the bag is black. That marble from the bag is black. A third marble from the bag is black. Therefore all the marbles in the bag black.[6]
  • Two-thirds of my latino neighbors are illegal immigrants. Therefore, two-thirds of latino immigrants come illegally.
  • Most universities and colleges in Utah ban alcohol from campus. That most universities and colleges in the U.S. ban alcohol from campus.

Deduction and induction by themselves are inadequate to make a compelling argument. While deduction gives absolute proof, it never makes contact with the real world, there is no place for observation or experimentation, and no way to test the validity of the premises. And, while induction is driven by observation, it never approaches actual proof of a theory. Therefore an effective paper will include both types of logic.[7]

Critical Thinking and Logical Fallacies

Many of the texts you’ll read in college will rely heavily on logical arguments. Logic is highly valued as a way of persuading readers, since it can be confirmed to be true.

However, logic can be used badly. When you’re reading, you’ll want to be able to pick out bad logic as well as good logic. This video series helps us identify different types of “bad logic” in reading we might encounter.

Broken Logic

The Man Who Was Made of Straw

Getting Personal

The Gambler’s Fallacy

Have you encountered these types of bad logic, also called fallacies, in reading you’ve done so far? Once you’re aware of them, they start to appear before your eyes, in text and in advertising of all types.