Main Idea versus Controlling Idea

Topic sentences contain both a main idea (the subject, or topic that the writer is discussing) and a controlling idea (the writer’s specific stance on that subject). Just as a thesis statement includes an idea that controls a document’s focus, a topic sentence must also contain a controlling idea to direct the paragraph. Different writers may use the same main idea but can steer their paragraph in a number of different directions according to their stance on the subject. Read the following examples.

Although the main idea—marijuana—is the same in all three topic sentences, the controlling idea differs depending on the writer’s viewpoint.

Characteristics of a Good Topic Sentence

Five characteristics define a good topic sentence:

1. A good topic sentence provides an accurate indication of what the rest of the paragraph is about.

   Weak example. People rarely give firefighters the credit they deserve for such a physically and emotionally demanding job. (The paragraph is about a specific incident that involved firefighters; therefore, this topic sentence is too general.)

   Stronger example. During the October riots, Unit 3B went beyond the call of duty. (This topic sentence is more specific and indicates that the paragraph will contain information about a particular incident involving Unit 3B.)

2. A good topic sentence contains both a topic and a controlling idea or opinion.

   Weak example. In this paper, I am going to discuss the rising suicide rate among young professionals. (This topic sentence provides a main idea, but it does not present a controlling idea, or thesis.)

   Stronger example. The rising suicide rate among young professionals is a cause for immediate concern. (This topic sentence presents the writer’s opinion on the subject of rising suicide rates among young professionals.)

3. A good topic sentence is clear and easy to follow.

   Weak example. In general, writing an essay, thesis, or other academic or nonacademic document is considerably easier and of much higher quality if you first construct an outline, of which there are many different types. (This topic sentence includes a main idea and a controlling thesis, but both are buried beneath the confusing sentence structure and unnecessary vocabulary. These obstacles make it difficult for the reader to follow.)

   Stronger example. Most forms of writing can be improved by first creating an outline. (This topic sentence cuts out unnecessary verbiage and simplifies the previous statement, making it easier for the reader to follow.)

4. A good topic sentence does not include supporting details.

   Weak example. Salaries should be capped in baseball for many reasons, most importantly so we don’t allow the same team to win year after year. (This topic sentence includes a supporting detail that should be included later in the paragraph to back up the main point.)

   Stronger example. Introducing a salary cap would improve the game of baseball for many reasons. (This topic sentence omits the additional supporting detail so that it can be expanded upon later in the paragraph.)

5. A good topic sentence engages the reader by using interesting vocabulary.

   Weak example. The military deserves better equipment. (This topic sentence includes a main idea and a controlling thesis, but the language is bland and unexciting.)

   Stronger example. The appalling lack of resources provided to the military is outrageous and requires our immediate attention. (This topic sentence reiterates the same idea and controlling thesis, but adjectives such as appalling and immediate better engage the reader. These words also indicate the writer’s tone.)

An effective paragraph contains three main parts: a topic sentence, the body, and the concluding sentence. A topic sentence is often the first sentence of a paragraph. It expresses a main idea combined with the writer’s attitude about the subject. The body of the paragraph usually follows, containing supporting details. Supporting sentences help explain, prove, or enhance the topic sentence. The concluding sentence is the last sentence in the paragraph. It reminds the reader of the main point by restating it in different words.

Paragraph Structure

• Topic Sentence (main idea + personal opinion)
• Body 
• Supporting Sentence
• Supporting Sentence
• Supporting Sentence
• Conclusion (summary of main idea + personal opinion)

Exercise 2

Identify the topic sentence, supporting sentences, and concluding sentence in the following paragraph.

Supporting Sentences

If you think of a paragraph as a hamburger, the supporting sentences are the meat inside the bun. They make up the body of the paragraph by explaining, proving, or enhancing the controlling idea in the topic sentence. Most paragraphs contain three to six supporting sentences depending on the audience and purpose for writing. A supporting sentence usually offers one of the following:

• Reason

  Sentence: The refusal of the baby boom generation to retire is contributing to the current lack of available jobs.

• Fact

  Sentence: Many families now rely on older relatives to support them financially.

• Statistic

  Sentence: Nearly 10 percent of adults are currently unemployed in the United States.

• Quotation

  Sentence: “We will not allow this situation to continue,” stated Senator Johns.

• Example

  Sentence: Last year, Bill was asked to retire at the age of fifty-five.

The type of supporting sentence you choose will depend on what you are writing and why you are writing. For example, if you are attempting to persuade your audience to take a particular position you should rely on facts, statistics, and concrete examples, rather than personal opinions. Read the following example:

Concluding Sentences

An effective concluding sentence draws together all the ideas you have raised in your paragraph. It reminds readers of the main point—the topic sentence—without restating it in exactly the same words. Using the hamburger example, the top bun (the topic sentence) and the bottom bun (the concluding sentence) are very similar. They frame the “meat” or body of the paragraph. Compare the topic sentence and concluding sentence from the previous example:

Notice the use of the synonyms advantages and benefits. The concluding sentence reiterates the idea that owning a hybrid is advantageous without using the exact same words. It also summarizes two examples of the advantages covered in the supporting sentences: low running costs and environmental benefits.

You should avoid introducing any new ideas into your concluding sentence. A conclusion is intended to provide the reader with a sense of completion. Introducing a subject that is not covered in the paragraph will confuse the reader and weaken your writing.

A concluding sentence may do any of the following:

• Restate the main idea.

  Example: Childhood obesity is a growing problem in the United States.

• Summarize the key points in the paragraph.

  Example: A lack of healthy choices, poor parenting, and an addiction to video games are among the many factors contributing to childhood obesity.

• Draw a conclusion based on the information in the paragraph.

  Example: These statistics indicate that unless we take action, childhood obesity rates will continue to rise.

• Make a prediction, suggestion, or recommendation about the information in the paragraph.

  Example: Based on this research, more than 60 percent of children in the United States will be morbidly obese by the year 2030 unless we take evasive action.

• Offer an additional observation about the controlling idea.

  Example: Childhood obesity is an entirely preventable tragedy.

Transitions

A strong paragraph moves seamlessly from the topic sentence into the supporting sentences and on to the concluding sentence. To help organize a paragraph and ensure that ideas logically connect to one another, writers use transitional words and phrases. A transition is a connecting word that describes a relationship between ideas. Take another look at the earlier example:

Useful Transitional Words and Phrases

Key Takeaways

• A good paragraph contains three distinct components: a topic sentence, body, and concluding sentence.
• The topic sentence expresses the main idea of the paragraph combined with the writer’s attitude or opinion about the topic.
• Good topic sentences contain both a main idea and a controlling idea, are clear and easy to follow, use engaging vocabulary, and provide an accurate indication of what will follow in the rest of the paragraph.
• Topic sentences may be placed at the beginning, middle, or end of a paragraph. In most academic essays, the topic sentence is placed at the beginning of a paragraph.
• Supporting sentences help explain, prove, or enhance the topic sentence by offering facts, reasons, statistics, quotations, or examples.
• Concluding sentences summarize the key points in a paragraph and reiterate the main idea without repeating it word for word.
• Transitional words and phrases help organize ideas in a paragraph and show how these ideas relate to one another.