In the Digital SAT Reading and Writing section, the "Craft and Structure" domain accounts for approximately 28% of your total score. Within this domain, "Text Structure and Purpose" questions are a vital component. While "Main Idea" questions ask you what the text is about, "Author’s Purpose" questions ask you why the author wrote it or why they included a specific piece of information.
This skill is fundamental because the SAT is no longer a test of long-form reading endurance; it is now a test of precision and rhetorical analysis. On the Digital SAT, you will encounter short passages (25–150 words) followed by a single question. For "Purpose" questions, the prompt usually asks: "Which choice best describes the main purpose of the text?" or "Which choice best describes the function of the underlined sentence in the text as a whole?"
You can expect to see roughly 3 to 4 of these questions per module. Because these questions appear in the first half of the Reading and Writing section, they set the tone for your performance. Mastering this skill means moving beyond literal comprehension and beginning to see the text as a tool used by an author to achieve a specific goal—whether that goal is to challenge a long-held scientific theory, characterize a fictional protagonist’s internal conflict, or illustrate a complex historical trend.
At the "Medium" difficulty level, the SAT moves away from obvious purposes (like "to tell a story") and toward more nuanced rhetorical moves (like "to qualify a previous claim" or "to provide context for a specific finding"). This guide will teach you how to decode the author's intent by focusing on structural cues, tone, and the relationship between ideas.
Core Concepts
To master Author’s Purpose, you must shift your mindset from a "reader" to a "literary critic." You aren't just absorbing information; you are analyzing the architecture of the argument.
1. The "Verb + Content" Formula
Every correct answer choice for a Purpose question follows a specific formula: [Strong Rhetorical Verb] + [Accurate Summary of Content].
- The Verb: This describes the action the author is taking (e.g., illustrate, criticize, acknowledge, reconcile, hypothesize).
- The Content: This describes what the author is talking about (e.g., the limitations of a study, the beauty of a landscape, the complexity of a mathematical proof).
If the verb is wrong (e.g., the choice says "criticize" but the author is actually "praising"), the answer is wrong. If the content is wrong (e.g., the choice says "describes a bird" but the text is about "a mammal"), the answer is wrong. Both halves must be 100% accurate.
2. Distinguishing Between Main Purpose and Specific Function
There are two primary ways the SAT tests this skill:
- Main Purpose of the Text: This asks for the "Why" of the entire passage. You must look at the relationship between the first and last sentences. Does the author start with a problem and end with a solution? The purpose is to propose a solution. Does the author start with a theory and end with evidence that disproves it? The purpose is to challenge a theory.
- Function of a Detail/Sentence: This asks why a specific part exists. Often, a sentence serves as a "pivot" (changing the direction of the argument), "evidence" (supporting a previous claim), or "context" (providing background information needed to understand the main point).
3. Identifying Rhetorical Moves
High-scoring students look for "moves" the author makes. Common moves include:
- The Pivot: The author introduces a common belief ("Many scientists argue...") and then uses a transition word like however or nonetheless to introduce their own, different view. The purpose here is often to "challenge a consensus."
- The General-to-Specific: The author starts with a broad statement about a topic and then provides a specific example or case study. The purpose is to "illustrate a general principle through a specific instance."
- The Acknowledgment/Concession: The author admits that a counterargument has some merit before explaining why their own point is still stronger. The purpose is to "qualify a claim" or "acknowledge a potential limitation."
4. Tone and Neutrality
In Medium-difficulty questions, the SAT often uses neutral, academic language. If a passage is a straightforward report on a scientific discovery, the purpose is likely to "describe," "inform," or "present." If the passage contains evaluative adjectives (e.g., extraordinary, flawed, shortsighted, brilliant), the purpose will involve "praising" or "critiquing."
5. Abstract vs. Concrete
The SAT often uses "abstract" language in the answer choices to describe "concrete" actions in the text.
- Concrete Text: "The telescope used a 10-meter mirror to capture light from the Andromeda galaxy."
- Abstract Answer Choice: "The author provides technical details to emphasize the capability of a scientific instrument."
Learning to translate the specific details of the text into the abstract language of the answer choices is the key to moving from a 600 to a 700+ score.
SAT Strategy Tips
1. The "Cover and Predict" Method
Before looking at the answer choices, read the passage and ask yourself: "What is the author trying to do here?" Write down a 3-5 word "Pre-diction." For example: "Prove the old theory wrong" or "Describe a character's sadness." Matching your prediction to an answer choice prevents you from being swayed by "distractor" choices that look plausible but are technically incorrect.
2. Focus on the First Verb
When scanning answer choices, look at the first word of each choice.
- If the text is a neutral description, eliminate choices starting with advocate, criticize, or persuade.
- If the text is an argument, eliminate choices starting with list, summarize, or depict. This "vertical scanning" saves time and narrows your focus immediately.
3. The "Whole Text" Rule
For "Main Purpose" questions, the correct answer must cover the entire passage. A common trap is a choice that accurately describes only the first sentence or only the last sentence. If a choice is too narrow, it is incorrect.
4. Time Management
You should aim to spend about 70–80 seconds on these questions. Spend 40 seconds reading and analyzing the structure, and 30 seconds evaluating the choices. If you are stuck between two choices, check the "Content" half of the Verb + Content formula—usually, one choice will contain a small factual error regarding the text's details.
Worked Example: Easy (Literature
The following text is from Lucy Maud Montgomery’s 1908 novel, Anne of Green Gables.
"Matthew enjoyed the drive after his own fashion. It was a pleasant drive through a valley of farms and woodland, with the June twilight closing in around them and the air full of the fragrance of clover fields. Matthew spoke little, but he listened with a quiet smile to Anne’s constant chatter, feeling a sense of warmth he had not expected."
Which choice best describes the main purpose of the text? A) To argue that Matthew is a better listener than a talker. B) To provide a description of a setting that reflects a character’s internal state. C) To establish a contrast between the peaceful environment and a character’s anxiety. D) To characterize the beginning of a positive rapport between two individuals.
Reasoning:
- Correct Answer: D. The text describes Matthew enjoying the drive and listening to Anne with a "quiet smile" and "warmth." This illustrates the start of a friendly, positive relationship (rapport) between them.
- Why A is wrong: While Matthew "spoke little," the text isn't making an "argument" about his skills; it's describing a specific moment.
- Why B is wrong: The setting is described as pleasant, but the primary focus is on the interaction between Matthew and Anne, not just the setting's reflection of his mood.
- Why C is wrong: There is no "anxiety" mentioned; the mood is entirely peaceful and warm.
Worked Example: Medium (Science
In a 2021 study, marine biologist Dr. Elena Rossi examined the vocalizations of humpback whales during migration. While previous researchers had hypothesized that these songs served primarily as mating calls, Rossi observed that the songs changed in frequency and duration when the whales encountered shifts in ocean temperature. This suggests that the vocalizations may also function as a form of environmental sonar, helping the pods navigate changing thermoclines.
Which choice best describes the function of the underlined sentence in the text as a whole? A) It presents a hypothesis that the study’s findings ultimately support. B) It introduces a traditional view that the study’s findings call into question. C) It provides evidence that contradicts the main conclusion of Dr. Rossi’s research. D) It outlines the methodology used by previous researchers in the field.
Reasoning:
- Correct Answer: B. The underlined sentence mentions what "previous researchers had hypothesized" (mating calls). The next sentence starts with "While..." and shows Rossi found something different (environmental sonar). Therefore, the underlined sentence is the "traditional view" that Rossi’s findings "call into question" (challenge).
- Why A is wrong: Rossi’s findings do not support the mating call hypothesis; they suggest a different purpose.
- Why C is wrong: The sentence doesn't contradict Rossi's conclusion; it provides the context that Rossi's conclusion is meant to update or change.
- Why D is wrong: The sentence mentions a hypothesis (a theory), not a methodology (the "how" of the experiment).
Worked Example: Hard (Social Science/History
Historian Marcus Thorne’s recent analysis of 19th-century labor movements suggests that the success of strikes was less dependent on the size of the union than on the timing of the action relative to the harvest season. However, Thorne’s work primarily focuses on agrarian societies, leaving open the question of whether this "seasonal dependency" holds true for the industrial urban centers of the same era, where production cycles were dictated by steam power rather than the sun.
Which choice best describes the main purpose of the text? A) To summarize a new historical theory and identify a potential limitation of its current scope. B) To criticize a historian for failing to consider the impact of industrialization on labor movements. C) To reconcile two competing theories regarding the success of 19th-century labor strikes. D) To explain how the introduction of steam power changed the nature of labor union organization.
Reasoning:
- Correct Answer: A. The first sentence summarizes Thorne’s "new historical theory" (harvest timing vs. union size). The second sentence (starting with "However") identifies a "limitation" (it only focuses on agrarian societies and might not apply to cities).
- Why B is wrong: The tone is not "critical." It neutrally points out what the work "primarily focuses on" and what "remains open." "Criticize" is too strong.
- Why C is wrong: There are no "competing theories" presented; only Thorne’s theory is discussed.
- Why D is wrong: While steam power is mentioned, the purpose of the text isn't to explain the history of steam power; it's to discuss the scope of Thorne’s research.
Practice Problems
Problem 1
The following text is adapted from a 1920 essay by Agnes Repplier.
"To be a good talker, one must be a good listener; and to be a good listener, one must have a certain amount of sympathy and a great deal of patience. It is not enough to be silent. Silence can be a very cold and discouraging thing. One must be 'attentive,' which means that the mind must be alert to follow the speaker’s thought, and the heart must be ready to respond to the speaker’s feelings."
Which choice best describes the main purpose of the text? A) To argue that silence is the most important component of effective communication. B) To define the specific qualities that constitute active and empathetic listening. C) To compare the conversational styles of different social groups in the early 20th century. D) To suggest that being a good talker is more difficult than being a good listener.
Problem 2
In 2018, astronomers detected an unusual dimming of the star KIC 8462852, also known as "Tabby’s Star." While some popular media outlets speculated that the dimming was caused by a massive alien structure, a team led by Tabetha Boyajian utilized multi-wavelength photometry to analyze the light. They found that certain colors of light were blocked more than others, a pattern consistent with clouds of fine dust rather than a solid, opaque object.
Which choice best describes the function of the underlined sentence in the text as a whole? A) It describes the primary data collection method used by Boyajian’s team. B) It presents a sensationalized explanation that the researchers aimed to investigate. C) It offers a definitive conclusion that the rest of the passage seeks to prove. D) It acknowledges a popular theory that the researchers' findings eventually confirmed.
Problem 3
Many ecologists have long assumed that the introduction of non-native species into an ecosystem inevitably leads to a decrease in local biodiversity. However, a meta-analysis conducted by Dr. Sarah Knutie suggests that in certain island environments, non-native species can actually fill ecological niches left vacant by extinct native species, sometimes even facilitating the growth of remaining native flora by improving soil nutrient density.
Which choice best describes the main purpose of the text? A) To advocate for the intentional introduction of non-native species into island ecosystems. B) To describe a study that supports a long-standing assumption in the field of ecology. C) To present research that complicates a common understanding of non-native species. D) To discuss the specific soil nutrients that are most beneficial to island flora.
Want to check your answers and get step-by-step solutions?
Common Mistakes
1. Choosing "Main Idea" instead of "Purpose"
- The Mistake: Selecting an answer that simply summarizes the text.
- The Fix: If the question asks for "purpose," ensure your choice explains why the author wrote it. If the text says "The sky is blue," the main idea is "the color of the sky," but the purpose might be "to describe a visual phenomenon."
2. Ignoring the "Pivot"
- The Mistake: Focusing only on the first half of the passage.
- The Fix: Many SAT passages start with one idea ("Many people believe X...") and then switch to the main point ("...but actually Y"). The purpose is almost always related to "Y," not "X." Look for words like however, but, yet, conversely, and nonetheless.
3. Misinterpreting the Tone
- The Mistake: Choosing an answer with a strong verb like "denounce" or "advocate" for a neutral, scientific text.
- The Fix: Match the intensity of the answer choice's verb to the intensity of the text. If the text is objective and data-driven, the purpose verb should be neutral (e.g., present, describe, summarize).
4. Falling for "Too Broad" or "Too Narrow" Choices
- The Mistake: Picking an answer that only covers one sentence (too narrow) or an answer that discusses a topic not mentioned in the text (too broad).
- The Fix: Perform a "check-off." Does the answer choice account for the beginning, middle, and end of the passage? If not, keep looking.
Frequently Asked Questions
What should I do if two answer choices both seem to describe the purpose correctly?
A: Look at the specific nouns and verbs. The SAT is famous for "half-right, half-wrong" answers. One choice might have the right verb ("To illustrate...") but the wrong object ("...a historical conflict" when the text was about a "scientific conflict"). The correct answer must be 100% accurate in every word.
How do I handle "Purpose" questions for old literature passages?
A: Don't get bogged down in the old-fashioned vocabulary. Focus on the relationships between characters or the shift in mood. Usually, the purpose of a literature snippet is to "characterize" someone or "establish a setting." Look for the emotional "charge" of the passage (is it positive, negative, or tense?).
Should I read the question before the passage?
A: Yes. On the Digital SAT, knowing whether you are looking for the "Main Purpose" or the "Function of an Underlined Sentence" changes how you read. If it's a "Function" question, you can focus more heavily on how that specific sentence connects to the ones immediately before and after it.
Key Takeaways
Think Rhetorically: Ask "Why did the author write this?" rather than "What is this about?"
Verb + Content: Every correct answer must have an accurate action verb and an accurate description of the subject matter.
Identify the Pivot: Watch for transition words (however, but) that signal a change in purpose.
Abstract Translation: Be prepared for the answer choices to use "big words" (like concede or illustrate) to describe simple actions in the text.
Check the Scope: The main purpose must reflect the entire passage, not just a single detail.
Tone Match: Ensure the "attitude" of the answer choice matches the "attitude" of the author.