How to Find the Main Idea of a Passage

The main idea is usually stated in one sentence — most often the first or the last of the paragraph — and everything else in the paragraph supports it. Test a candidate sentence by asking whether the rest of the paragraph explains, proves or illustrates it. If it does, you have found the main idea; if not, keep looking.

The format

The main idea is usually stated, not hidden

In expository writing the main idea of a paragraph is normally stated outright in one sentence, called the topic sentence, and everything else in the paragraph explains, proves or illustrates it. Most often it is the first sentence; the next most common position is the last.

The test

Pick a candidate sentence and ask: does the rest of the paragraph explain, prove or illustrate this? If yes, it is the main idea. If the rest of the paragraph says something the candidate does not cover, keep looking.

• A sentence containing an example is almost never the main idea.
• A sentence beginning For instance, For example or Such as is support, not the idea.
• A sentence beginning But, However or Yet often carries the main idea, because the writer is correcting what came before.
• If the paragraph is a narrative rather than an argument, the main idea is what changed.

When it is not stated

Occasionally a paragraph implies its main idea without stating it. Then you must construct the sentence yourself: read the paragraph, ask what all the sentences are collectively about, and write that in one sentence of your own. This is harder, and it is where the marks separate.

From main ideas to a summary

Once each paragraph has one main-idea sentence, a summary is close to written. Put the sentences in order, in your own words, and add the connecting words the sequence needs. If the result reads as a list, the connections are what is missing.

Model answer

Worked example

Paragraph

The bicycle has never been improved upon as a way of moving one person a short distance. It costs a fraction of what any motor vehicle costs to buy and almost nothing to run. It takes up little road space and no fuel. For instance, a family in a small town can keep three bicycles for less than the annual running cost of a single motorcycle, and can park all three where one motorcycle would stand. It does not pollute. And unlike every alternative, using it makes the user healthier rather than less healthy.

Working it out

The first sentence is a candidate. Test it: cost, road space, fuel, the family example, pollution and health are all reasons why the bicycle has not been improved upon — so yes, the rest of the paragraph supports it. The sentence beginning "For instance" is an illustration and can be dropped entirely.

Main idea, in your own words

For short single-person journeys the bicycle remains unmatched, being cheap, space-efficient, clean and good for the rider.

What earns and loses marks

• Check the first sentence first. In expository prose it is the topic sentence more often than any other position.
• Any sentence beginning “For instance” or “For example” is support and can be deleted without loss.
• A sentence beginning “But” or “However” often carries the real idea — the writer is turning against what came before.
• If two sentences both seem to be the main idea, the paragraph probably has two, and your summary needs both.
• Write the main idea in your own words as soon as you find it; the summary is then half done.