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2.4  Analyzing Tasks: What is the Controlling (Central or Main) Idea?

The controlling idea (central idea or main idea) comes from the purpose and the subject. It gives readers a map of the essay's territory, a framework in which to interpret the specific material the essay will present. It gives writers a basis for decision-making: every sentence, every paragraph in the essay should be directly related to the controlling idea. In math terms, you might say:

controlling idea = purpose x subject x your point of view.

If you thought the purpose of this essay was to give information, you didn't understand the task. The purpose was to persuade the principal to let your club hold the dance in the school. Your job wasn't to inform the principal; your job was to get him or her to do to change the rules.

If you think of the topic of a selection as a subject, then the controlling (main or central) idea of that selection is the most important thing said about the subject or topic. Let's say we have an article to read in health class. The subject or topic of the article is a well-balanced diet. The controlling (main or central) idea of the article can be expressed in this sentence: A well-balanced diet is a key to good health.

In the third paragraph of the article is this sentence: Eating enough fruits and vegetables every day is important to having a well-balanced diet. Is this the controlling idea for the article?

No. It is the topic sentence for that paragraph of supporting detail, which will, no doubt, go on to tell of the varieties of fruits and vegetables and the benefits of eating them. The main idea or the controlling idea or the central idea is still expressed in the sentence, A well-balanced diet is a key to good health.

Just as a large company might have many department heads but only one CEO, the reading selection can have many topic sentences but only one controlling idea.
One Topic, Many Controlling Ideas
Another important rule to remember is that there can be many different controlling ideas about the same topic. The examples below show that the same general topic, swimming, can be the basis for persuasive, informational, and narrative controlling ideas. It is also important to note that there are different kinds of controlling ideas for different patterns and purposes.

Persuasive Writing's Purpose:
1. To prove a point or to recommend an action about a topic.
Opinion-Reason: Gives an opinion and recommends an action.

Controlling Idea (as an opinion): It is the responsibility of this school district to teach every child to swim.
2. To prove a point or to recommend an action about a topic.
Thesis-Proof: Proves a point and suggests or implies its significance.

Controlling Idea (as a thesis): Swimming is the most effective and most injury-free aerobic exercise you can do.
Informational Writing's Purpose: to give information about a topic.
1. How-To: Gives instructions or directions.

Controlling Idea (as the motivation for a how-to): With a half hour's practice, you can learn to swim the breast stroke so effortlessly that you could swim for an hour without stopping.
2. Topic-Aspect: Tells features.
Controlling Idea (as a statement of the topic): In competitive swimming, the individual medley consists of four parts.
Narrative Writing's Purpose:
To tell a series of events that show something about a topic-often, the controlling idea is implied rather than expressed.

Controlling Idea (as inferred from a story): It is dangerous to swim alone.

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