Why did the author write the material you are reading? To inform you? To persuade you? To motivate you? What particular issue does the text cover? In the margin, write down what you think the author’s purpose is. It will be related to, but not exactly the same as, the main idea.
The main idea is a specific idea that supports the author’s broader purpose. Often, the first sentence clues you in to the main idea, or topic; sometimes, the first sentence is a straightforward statement of the topic. However, don’t count on that. A writer may choose to leave the main idea unstated, expecting you to draw your own conclusions from the evidence and arguments assembled in the passage.
Think of the main idea as the spine of the passage; it is the long line that holds everything together.
Look for a statement of the main idea; if you find it, underline it. If there doesn’t seem to be a sentence that sums up the topic, write your own statement of the main idea in the margin.
If the main idea is the spine of the passage, the paragraph topics are the bones; they provide the underlying structure. Each paragraph adds something slightly different to the author’s argument; the supporting element contained in a paragraph is the paragraph topic. As with the main idea, paragraph topics may or may not be directly stated.
After you finish each paragraph, look for its topic sentence and underline it. If you can’t find a topic sentence, write your own statement in the margin.
So far, we have the skeleton of a passage, with the basic substructure of main idea and paragraph topics in place. But it is still a bit flimsy. That’s why the author adds key points or details. The key points are the muscles attached to that skeleton, making it stronger and more stable. These key points can be examples or logical arguments, but they have to be directly connected to the paragraph topic they flesh out.
The key points are always directly stated; otherwise, they wouldn’t be very useful. Number the key points the author gives to build up the paragraph topics. You will always have more key points than anything else. After all, there can be only one main idea per passage, and one paragraph topic per paragraph. But within a single paragraph, the author may provide several supporting points.