Strengthen | Varsity Tutors

SECTION 1

Historical Context & Motivation

The Law School Admission Test (LSAT) has served as the primary gatekeeper for law school admissions in the United States and Canada for over seven decades. Among its most analytically demanding components is the Logical Reasoning section, which assesses a test-taker's ability to evaluate, construct, and deconstruct arguments—skills that mirror the rigorous analytical reasoning required in legal practice. Within this section, Strengthen questions occupy a central role, requiring examinees to identify new information that makes a given argument's conclusion more likely to be true. Understanding the evolution of these question types provides essential context for mastering them.

1948

LSAT Inception

The Law School Admission Council (LSAC) administers the first LSAT, initially focusing on reading comprehension and quantitative reasoning. Formal argumentation analysis is not yet a standalone component.

1982

Logical Reasoning Formalized

LSAC restructures the exam to include dedicated Logical Reasoning sections, reflecting the legal academy's growing emphasis on informal logic. Strengthen and weaken question types become recurring features.

1991

Question Taxonomy Solidifies

Test-preparation research identifies approximately fifteen distinct Logical Reasoning question types. Strengthen questions are recognized as among the most frequently appearing, comprising roughly 10–15% of all LR questions per administration.

2007

Comparative Stimuli Introduced

LSAC introduces comparative reading passages and increasingly complex argument structures, raising the sophistication of strengthen questions by embedding more nuanced assumptions.

2019–Present

Digital LSAT Era

The transition to digital administration maintains the same logical rigor. Strengthen questions continue to appear with high frequency, and modern test-prep analytics reveal that they are among the most consistently challenging for unprepared examinees.

The enduring prominence of strengthen questions reflects a straightforward pedagogical reality: lawyers must constantly assess whether new evidence supports or undermines a legal position. The fundamental question a strengthen problem asks—which answer choice, if true, most supports this conclusion?—mirrors the evaluative judgment at the heart of legal reasoning. The remainder of this lesson equips you with a systematic framework for answering these questions with precision and confidence.

SECTION 2

Core Principles & Definitions

Before dissecting strengthen questions, it is essential to establish a precise vocabulary for the anatomy of an LSAT argument. Every argument on the Logical Reasoning section consists of identifiable structural components, and your ability to isolate these components determines your success. An argument on the LSAT is not a dispute between two parties; rather, it is a set of premises offered in support of a conclusion. The logical space between the premises and the conclusion—the unstated inferential leap the author makes—constitutes the assumption. A strengthen answer choice works by buttressing this assumption, thereby making the conclusion more probable given the stated evidence.

Premise

The explicitly stated evidence or facts the author offers. Premises are taken as true on the LSAT; you never question their accuracy. Your task is to evaluate the inferential link between premises and conclusion.

Conclusion

The claim the author asserts on the basis of the premises. It is the point the argument aims to prove. Identifying the conclusion accurately is the single most important step in tackling any strengthen question.

Assumption (Gap)

The unstated bridge between premise and conclusion. The assumption is what the author must believe to be true for the argument to hold. Strengthen answers supply evidence that validates or reinforces this assumption.

Strengthen (The Task)

To strengthen an argument is to provide additional information that increases the likelihood of the conclusion being true. The correct answer does not need to prove the conclusion—it merely needs to make it more probable.

The "If True" Proviso

Strengthen question stems typically include the phrase "if true" or "if valid." This instructs you to treat every answer choice as a hypothetically true statement. Do not evaluate the plausibility of the answer choices themselves.

✦ KEY TAKEAWAY

Think of an LSAT argument like a bridge. The premises are one riverbank, the conclusion is the other, and the assumption is the bridge structure itself—often invisible or incomplete. A strengthen answer acts like adding a steel support beam beneath the bridge: it does not build a second bridge, but it makes the existing crossing more secure. Your job is to find the answer choice that most effectively reinforces the structural integrity of that inferential bridge.

SECTION 3

Visual Explanation — Anatomy of a Strengthen Question

The diagram above illustrates the structural relationship between premises, conclusion, and the assumption gap. A strengthen answer (green) targets the assumption directly, reinforcing the inferential link. The bottom panel shows the four most common trap answer types that examinees must learn to eliminate.

As the diagram makes clear, the correct answer on a strengthen question is one that provides new evidence in support of the assumption. It is not enough for an answer choice to be generally positive or vaguely related to the topic of the stimulus. The correct answer must have a demonstrable logical connection to the gap between the stated premises and the conclusion. This is why your first analytical move should always be to articulate the assumption in your own words before reviewing the answer choices. If you can name the gap, you can identify the answer that fills it.

SECTION 4

How Strengthen Arguments Work — The Logical Mechanism

Although the LSAT does not require formal symbolic logic, understanding the underlying logical mechanism of strengthen questions sharpens your analytical precision. Every LSAT argument can be modeled as an informal inference: given evidence E, the author concludes C. The assumption A is the unstated conditional that links E to C. A strengthen answer S operates by providing additional evidence that makes it more probable that A holds, thereby increasing the probability of C given E. In formal terms, the correct answer raises P(C | E ∧ S) relative to P(C | E) alone.

The Assumption Bridge Model

ARGUMENT STRUCTURE

Premises (E) + Assumption (A) → Conclusion (C)

Where E = explicitly stated evidence, A = the unstated necessary or sufficient assumption, and C = the author's conclusion.

STRENGTHEN OPERATION

P(C | E ∧ S) > P(C | E)

The correct strengthen answer S increases the conditional probability of the conclusion. Note that S does not need to guarantee C; it merely needs to shift the probability upward.

Five Mechanisms by Which an Answer Can Strengthen

Validates the Assumption

The most direct mechanism: the answer choice explicitly affirms the unstated link between premises and conclusion. If the argument assumes that X causes Y, the correct answer might provide direct evidence of the causal mechanism.

Eliminates an Alternative Cause

In causal arguments, the correct answer may rule out a plausible competing explanation. By showing that alternative cause Z is not operative, the answer makes it more likely that the author's proposed cause is correct.

Provides Additional Evidence

The answer introduces a new data point or fact that, while not directly affirming the assumption, provides corroborating evidence consistent with the conclusion. This is common in arguments involving statistical or empirical claims.

Removes a Potential Objection

Some strengthen answers work defensively: they preempt a likely objection to the argument. By showing that a foreseeable counterargument fails, the answer indirectly bolsters the conclusion.

Establishes a Necessary Condition

If the conclusion requires certain preconditions, the answer may confirm that those preconditions are met. This is particularly relevant in arguments involving policy recommendations or predictions.

⚠️ Critical Distinction

A strengthen answer does not need to prove the conclusion beyond doubt—it only needs to make the conclusion somewhat more likely. This is a common source of error for test-takers who dismiss a correct answer because it seems insufficient. On the LSAT, even a marginal increase in probabilistic support qualifies as strengthening.

SECTION 5

Recognizing and Classifying Strengthen Question Stems

Your ability to recognize a strengthen question begins with the question stem—the prompt that appears after the stimulus and directs you to your analytical task. The LSAT employs a range of phrasings for strengthen questions, and familiarity with these variants ensures you do not misidentify the question type. Below is a comprehensive classification of strengthen stem language, organized by frequency of appearance.

This taxonomy organizes strengthen question stems by their frequency of appearance on recent LSAT administrations. Note the three key signal words at the bottom: strengthens/supports/justifies (identifies the task), if true (the acceptance proviso), and most (the comparative standard).

An important but sometimes overlooked variant is the "EXCEPT" strengthen question, in which four of the five answer choices strengthen the argument and you must identify the one that does not. These questions are rarer but particularly challenging because they require you to evaluate all five choices thoroughly rather than stopping after finding one that works. When you see "Each of the following strengthens the argument EXCEPT," your task inverts: you are looking for the answer that is neutral, irrelevant, or weakening.

Common strengthen stem variants and their associated traps

Stem Phrasing	Your Task	Key Trap to Avoid
"most strengthens the argument"	Find the answer that best supports the conclusion	Selecting an answer that merely restates a premise
"most supports the claim above"	Identify the specific claim and target it	Supporting a subsidiary claim rather than the main conclusion
"most helps to justify"	Find evidence that validates the reasoning	Confusing justification with explanation
"Each strengthens EXCEPT"	Find the one answer that does NOT strengthen	Forgetting the inversion and selecting a strengthener

SECTION 6

Worked Example — Full Strengthen Question

📄 STIMULUS

A city council recently installed solar-powered streetlights in a downtown district as part of a pilot energy-efficiency program. In the six months following the installation, the district experienced a 30 percent reduction in nighttime crime. The council concluded that the solar-powered streetlights were responsible for the reduction in crime.

❓ QUESTION STEM

Which one of the following, if true, most strengthens the city council's argument?

📋 ANSWER CHOICES

(A) Solar-powered streetlights are less expensive to maintain than traditional streetlights. (B) The police department did not increase patrols in the downtown district during the six-month period. (C) Other districts in the city that did not receive new streetlights experienced similar reductions in nighttime crime. (D) The solar-powered streetlights produce a brighter light than the traditional streetlights they replaced. (E) The city council plans to expand the solar-powered streetlight program to other districts next year.

Step-by-Step Solution

Step 1 — Identify the ConclusionThe council concluded that the solar-powered streetlights were responsible for the reduction in crime. This is a causal claim: the streetlights caused the crime decrease.

Conclusion: Solar streetlights caused the 30% crime reduction.

Step 2 — Identify the PremisesTwo facts are provided: (1) solar-powered streetlights were installed, and (2) nighttime crime dropped 30% in the following six months. These are the stated evidence.

Premises: Installation occurred → Crime decreased 30%.

Step 3 — Articulate the Assumption (Gap)The argument assumes a causal relationship based on a temporal correlation. The gap is that the author has not ruled out alternative explanations for the crime reduction. Perhaps increased police patrols, seasonal changes, or other concurrent programs contributed to the decrease. The assumption is that no other significant factor caused the crime reduction.

Assumption: No other factor caused the crime reduction.

Step 4 — Predict the Correct AnswerA correct strengthen answer should either (a) eliminate an alternative cause, (b) provide additional evidence of the causal link between lights and crime, or (c) confirm that a necessary condition for the causal claim was met. We should look for an answer that rules out a competing explanation.

Step 5 — Evaluate Each Answer Choice(A) — Maintenance cost is irrelevant to whether the lights reduced crime. This addresses economics, not causation. Eliminate. (B) — This rules out a significant alternative explanation: increased police patrols. If police patrols did not change, the crime reduction cannot be attributed to policing, which makes it more likely the streetlights were responsible. Strong contender. (C) — If districts without new streetlights also experienced crime reductions, this suggests a different factor was at play. This weakens the argument. Eliminate. (D) — While intriguing, brightness alone does not directly demonstrate that the streetlights reduced crime. It provides a possible mechanism but does not eliminate alternative causes as effectively as (B). Weaker than (B). (E) — Future plans are irrelevant to whether the current installation caused the crime reduction. Eliminate.

Correct Answer: (B) — By eliminating increased police patrols as an alternative explanation, this answer strengthens the causal claim that the streetlights were responsible.

🔑 PATTERN RECOGNITION

This question exemplifies the most common strengthen mechanism on the LSAT: eliminating an alternative cause. When the argument draws a causal conclusion from a correlation, the strongest answer is almost always one that rules out a plausible competing explanation. Develop the habit of asking: "What else could have caused this outcome?"—and then look for the answer that says, "That other thing didn't happen."

SECTION 7

Common Traps & How to Avoid Them

The LSAT is designed by psychometricians who understand the cognitive biases and reasoning errors test-takers commonly exhibit. Strengthen questions include carefully crafted distractor answer choices that exploit predictable mistakes. Recognizing these traps in advance is as important as understanding the correct answer pattern. The following table catalogues the most frequent trap types, their characteristics, and strategies for avoiding them.

Five common distractor types on LSAT Strengthen questions

Trap Type	Description	How to Identify It	Avoidance Strategy
Opposite (Weakener)	The answer actually undermines the conclusion. Test-takers select it because it seems relevant to the argument.	Ask: "Does this make the conclusion more or less likely?" If less, it's a weakener.	Always apply the Strengthen/Weaken test: mentally insert the answer and check the direction of its impact.
Irrelevant Scope	The answer discusses a topic tangentially related to the stimulus but has no logical bearing on the conclusion.	Check whether the answer addresses the specific gap between premises and conclusion. If it addresses a different issue, it's out of scope.	Pre-phrase the assumption before reviewing answers. If an answer doesn't connect to your pre-phrase, treat it with skepticism.
Premise Restatement	The answer simply rephrases information already stated in the stimulus. It adds no new support.	Compare the answer to the stimulus content. If the information is already present (even in different words), it cannot strengthen.	A strengthen answer must provide NEW information. Cross-reference each choice against the stimulus.
Wrong Conclusion	The answer supports a conclusion that is related to but different from the one actually drawn in the argument.	Verify that the answer supports the specific conclusion, not a generalized or adjacent claim.	Underline the exact conclusion in the stimulus and test each answer against those precise words.
Too Extreme	The answer uses absolute language ("always," "never," "all") that technically strengthens but is often a trap in other question types, causing test-takers to dismiss it.	Remember: on strengthen questions, extreme language can be correct because you accept the answer as true.	Apply the "if true" proviso rigorously. Even if the answer seems implausible in the real world, accept it as given.

🛡️ TRAP AVOIDANCE HEURISTIC

Think of distractor answer choices like decoy doors in an escape room: each one looks plausible at first glance because it relates to the room's theme, but only one actually leads out. The pre-phrase strategy is your flashlight—by articulating the assumption before reading the answer choices, you create a mental template that filters out irrelevant, opposite, and off-target options. The more specific your pre-phrase, the faster and more accurately you can identify the correct answer.

SECTION 8

Connection to Advanced Question Types

Strengthen questions do not exist in isolation within the LSAT's architecture; they belong to a family of question types that test your ability to evaluate the relationship between evidence and conclusions. Understanding how strengthen questions relate to their sibling types—Weaken, Assumption, and Flaw—deepens your analytical toolkit and enables strategic flexibility. The skills you develop on strengthen questions transfer directly to these related types because they all revolve around the same structural analysis: identifying premises, conclusions, and the gaps between them.

Comparative analysis: Strengthen vs. Weaken vs. Assumption question types

Dimension	Strengthen	Weaken	Assumption
Task	Add new info that supports the conclusion	Add new info that undermines the conclusion	Identify the unstated premise required for the argument to hold
Relationship to Gap	Fills or reinforces the gap	Exploits or widens the gap	IS the gap
Degree Required	Any marginal increase in probability	Any marginal decrease in probability	Necessary condition for the conclusion
"If True" Proviso	Present	Present	Not always present (but assumed)
Negation Test Applicable?	Not directly (use the Strengthen/Weaken directional test)	Not directly	Yes—negating a necessary assumption destroys the argument
Strategic Overlap	A strengthen answer is often a restatement of the assumption with additional evidence	A weaken answer is the negation of what a strengthen answer would provide	An assumption answer, if accepted as true, always strengthens the argument

One of the most valuable insights for advanced LSAT preparation is the Assumption–Strengthen–Weaken continuum. An assumption is the minimum condition the argument requires. A strengthen answer provides evidence that the assumption holds. A weaken answer provides evidence that the assumption fails. If you master assumption identification, you effectively gain proficiency across all three question types. This is why experienced test-takers prioritize assumption-spotting as the foundational skill for the entire Logical Reasoning section, viewing strengthen and weaken questions as applied extensions of the same analytical operation.

🎓 Forward-Looking Skill Transfer

In law school, the strengthen–weaken analytical framework maps directly to legal argumentation. When you draft a memorandum of law, you strengthen your client's position by adducing favorable precedent (analogous to validating the assumption) and preemptively addressing opposing arguments (analogous to eliminating alternative explanations). The LSAT is, in this sense, an introduction to the reasoning patterns you will employ throughout your legal career.

SECTION 9

Practice Problems

PROBLEM 1 — CONCEPTUAL

An LSAT argument concludes that a new medication is effective because patients who took it showed improvement. What is the primary assumption in this argument, and what type of strengthen answer would most directly support the conclusion?

PROBLEM 2 — BASIC

Stimulus: "A school district implemented a mandatory breakfast program for elementary students. Over the following academic year, standardized test scores in the district rose by 12 percent. Therefore, the breakfast program caused the improvement in test scores." Question stem: Which of the following, if true, most strengthens this argument? (A) The district also hired additional reading specialists during the same year. (B) Districts that did not implement breakfast programs saw no significant change in test scores. (C) Students reported feeling happier at school after the breakfast program began. (D) The breakfast program cost less than expected to implement. (E) Some students chose not to participate in the breakfast program.

PROBLEM 3 — INTERMEDIATE

Stimulus: "Research indicates that cities with more parks per capita tend to have lower rates of cardiovascular disease. Urban planners have therefore recommended that City X build additional parks in order to reduce the prevalence of cardiovascular disease among its residents." Question stem: Which of the following, if true, most strengthens the urban planners' recommendation? (A) City X currently has fewer parks per capita than most cities in the study. (B) Cardiovascular disease is the leading cause of death among City X's residents. (C) The study controlled for differences in income, age demographics, and access to healthcare across the cities surveyed. (D) City X has recently invested heavily in public health campaigns targeting cardiovascular disease. (E) Many residents of cities with more parks use them primarily for social gatherings rather than exercise.

PROBLEM 4 — APPLIED

Stimulus: "A technology company found that employees who were allowed to work remotely at least three days per week produced 20 percent more code commits than their in-office counterparts. The CEO argues that the company should shift to a predominantly remote work model to maximize overall productivity." Question stem: Which of the following, if true, most strengthens the CEO's argument? (A) Employees who work remotely report higher levels of job satisfaction. (B) The quality of code produced by remote workers, as measured by bug frequency, was at least as high as that produced by in-office workers. (C) Several competing technology companies have also adopted remote work policies. (D) The company's office lease is scheduled to expire within six months. (E) Some remote workers reported difficulty collaborating on team-based projects.

PROBLEM 5 — CRITICAL THINKING

Stimulus: "In every year since Country Z introduced a carbon tax, its national greenhouse gas emissions have declined. Critics attribute the decline to a broader global economic slowdown rather than the carbon tax. However, the government maintains that the carbon tax is the primary driver of reduced emissions." Question stem: Which of the following, if true, most strengthens the government's position? (A) Country Z's economy grew at an average rate of 3 percent annually during the period of declining emissions. (B) The revenue from the carbon tax has been used to fund renewable energy research. (C) Several other countries introduced carbon taxes during the same period with similar results. (D) Country Z's largest industrial sector voluntarily adopted emissions reduction targets before the tax was introduced. (E) Scientists predict that global temperatures will continue to rise regardless of emissions reductions.

SUMMARY

Lesson Summary

LSAT Strengthen questions ask you to identify new information that makes an argument's conclusion more likely to be true. Every argument consists of premises (stated evidence), a conclusion (the author's claim), and an assumption (the unstated inferential bridge). The correct answer reinforces the assumption through one of five mechanisms: validating the assumption directly, eliminating an alternative cause, providing additional corroborating evidence, removing a potential objection, or establishing a necessary condition.

Your systematic approach should follow a clear sequence: (1) identify the conclusion, (2) isolate the premises, (3) articulate the assumption gap, (4) pre-phrase a predicted answer, and (5) evaluate each choice against your pre-phrase. Guard against common traps: opposite answers (weakeners), irrelevant scope, premise restatements, and answers that support a wrong conclusion. Remember that strengthen questions exist on the Assumption–Strengthen–Weaken continuum: mastering assumption identification is the key to excelling across all three question types.