Reading comprehension question types - Main idea and primary...

Learning Outcomes

After reading this article, you will be able to identify and answer LSAT main idea and primary purpose questions with accuracy. You will understand how to spot the passage's central claim versus its details, distinguish author intent, and avoid common traps such as narrow or overly broad answer choices. You will also acquire essential techniques for solving these high-frequency LSAT question types efficiently.

LSAT Syllabus

For LSAT, you are required to understand the function and significance of reading comprehension big-picture questions. This article specifically focuses your revision on:

• recognising main idea and primary purpose questions in the reading comprehension section
• analysing answer choices for scope, accuracy, and relevance to the full passage
• using structural and language cues to identify an author’s overall point and intent
• differentiating between main point, author attitude, and topic
• applying elimination strategies to avoid common wrong answer patterns

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which of the following best defines the "main idea" of a passage?
   1. A single important detail
   2. The author's tone
   3. The primary argument spanning the entire passage
   4. An isolated supporting example
2. When asked for the "primary purpose" of a passage, you should:
   1. Focus on the most technical paragraph
   2. Identify the author's main goal in writing
   3. Summarize every supporting fact
   4. Find the longest answer
3. Which answer is LEAST likely to be correct for a main idea question?
   1. Too narrow, summarising only one section
   2. Overbroad, adding topics not found in the passage
   3. Directly addresses the entire passage
   4. Contradicts the author’s conclusion

4. True or false? You should form your own brief summary of the main point and purpose before reviewing answer choices.

Introduction

Main idea and primary purpose questions are central to the LSAT Reading Comprehension section. These big-picture question types assess your ability to extract what the author is arguing or seeking to achieve—goals that go beyond simply identifying surface details. You will see these question types frequently, often framed as "main point," "primary purpose," or "author's main concern."

Understanding the difference between main idea (what the author says overall) and primary purpose (why the author wrote it) is critical for selecting the correct answer choice.

Key Term: main idea
The overall argument or claim the author communicates throughout the entire passage. The main idea always encompasses more than any example or detail.

Key Term: primary purpose
The author's main intention for writing the passage—what the author seeks to accomplish, such as to argue, compare, criticise, or explain.

Types of Big-Picture Questions

Main idea and primary purpose questions use characteristic stems, such as:

• "Which one of the following most accurately summarizes the main point of the passage?"
• "The primary purpose of the passage is to..."
• "Which title best fits the passage?"
• "The author is primarily concerned with..."
• "The author's attitude can best be described as..."

Focus on these stems to identify when you are being asked for more than just a fact or small section.

How to Identify the Main Idea and Primary Purpose

To find the main idea:

• Ask: If you had to explain the entire passage in a single sentence, what would it be?
• Look for summary statements and conclusions, especially in the opening and closing paragraphs.
• Scan for structural signal words like "therefore," "in conclusion," or "however," which often highlight main points or author positions.

To determine the primary purpose:

• Evaluate the author's intent. Is the passage arguing, explaining, comparing, or warning?
• Check for purpose signal verbs in both the passage and question stem—words like "argue," "defend," "describe," "propose," or "compare."
• Distinguish between the purpose (WHY) and the topic (WHAT).

Key Term: scope
The defined range of the passage’s topic and claims. Staying within scope prevents you from choosing answers that are too narrow (covering only a paragraph) or too broad (adding unrelated claims).

Strategies for Answering

1. Make a brief summary in your own words as soon as you finish reading. This keeps you focused on the overall point, not confused by supporting details.
2. Use structure clues. Notice transition and summary indicators like "however," "finally," or "thus."
3. Anticipate the answer before looking at the choices. What is the single sentence that covers the argument and intent?
4. Avoid traps: Discard answers that cover only one paragraph, exaggerate, contradict, or introduce outside ideas.

Worked Example 1.1

Passage excerpt:
The author discusses two potential approaches to reducing air pollution: stricter car emission laws and new standards for building construction. Although both strategies are described, the author concludes that a broad regulatory policy is needed, not only piecemeal changes.

Question:
Which one of the following most accurately expresses the main point of the passage?

A) Car emissions should be regulated.
B) Only new building materials are effective.
C) Comprehensive regulation is necessary to address all sources of air pollution.
D) Air pollution cannot be reduced.
E) Building emissions have no impact.

Answer:
C expresses the main idea because it captures the passage’s focus on the necessity for broad regulations over isolated measures. A and B are too narrow; D directly contradicts the passage; E ignores major discussed topics.

Worked Example 1.2

Primary purpose question:
The passage describes a series of studies on animal migration and notes that recent findings have implications for climate policy. What is the primary purpose of the passage?

A) To explain new migration research
B) To advocate for migration-focused policymaking
C) To argue that climate policy must be informed by recent scientific studies
D) To describe migration patterns in detail
E) To outline the limitations of past research

Answer:
C states the author’s purpose—moving from presenting data to urging policy decisions. A and D are too narrow; B and E do not reflect the overall direction of the passage.

Common Traps to Avoid

• Scope errors: Reject answers that summarise only a supporting example or a minor issue.
• Overly strong or weak language: Extreme words like "always," "never," or "essential" rarely fit.
• Detail mistaken for argument: Support or data may sound important but is not the main idea or purpose.
• Misreading author intent: Do not confuse "describing" with "arguing" or "warning." Identify if the author is stating facts, recommending action, or criticising.
• Attitude vs. neutral summary: Ensure author’s tone matches—don't add positive/negative claims not present.

Revision Tip

For every LSAT Reading Comprehension passage, pause before answering big-picture questions and write a one-sentence summary of the main claim and why the author wrote the text.

Tactics for Eliminating Wrong Answers

• Read all answer choices; a later one may better reflect the passage’s focus.
• If two options remain, compare their accuracy, scope, and relevance to the entire text.
• Note classic wrong answer patterns: answers using verbatim text but not summarising the main argument, or answers that are too broad or too narrow.

Worked Example 1.3

Passage summary:
The passage outlines new regulations in the legal services market, mentioning lawyer opinions and predicted effects. The final paragraph criticises the plans, predicting negative effects for both lawyers and clients.

Question:
What is the primary purpose of the passage?

A) To criticise new legal regulation initiatives
B) To summarise opinions about legal plans
C) To report on an ongoing debate
D) To explain how legal plans impact prices
E) To recommend a particular legal service plan

Answer:
A is correct—the passage ends with the author’s evaluative criticism. Other answers either summarise part of the discussion or do not match the overall purpose.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Main idea questions are about the entire argument, not supporting details.
• For primary purpose, focus on what motivated the author to write, not just summary.
• Start every question of these types with your own summary sentence before checking answer choices.
• Choose answers matching the scope—avoid those too limited or overly broad.
• Extreme language and focus on illustrative details are classic LSAT traps.
• Look for transition and summary words to spot the structure and intent.

Key Terms and Concepts

• main idea
• primary purpose
• scope