Logical reasoning strategies and techniques - Deconstructing...

Learning Outcomes

After reading this article, you will be able to break down LSAT logical reasoning stimuli into their core parts, quickly spot premises and conclusions, and identify the structure of arguments. You will also understand how to distinguish argument statements from background facts, find implicit assumptions, and recognise common argument flaws. These skills are essential for tackling a wide range of LSAT Logical Reasoning questions effectively and confidently.

LSAT Syllabus

For LSAT, you are required to understand logical arguments from an analytical standpoint. This article focuses on the syllabus areas most frequently tested and fundamental to high performance in Logical Reasoning:

• Identifying the core structure of arguments in LSAT stimuli
• Distinguishing between premises, conclusions, and background facts
• Recognising implicit assumptions and hidden links
• Spotting common argument flaws and faulty reasoning
• Applying these strategies to strengthen, weaken, and assumption-type questions

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 statement best represents a conclusion?
   1. Evidence presented by the author
   2. The main point the author wants you to accept
   3. Statistical information only
   4. The first sentence in an argument
2. Which of the following is usually a premise indicator?
   1. However
   2. Therefore
   3. Because
   4. Nonetheless
3. What is an assumption in an LSAT argument?
   1. A claim that is explicitly stated
   2. Information repeated for emphasis
   3. A missing but necessary link between premises and the conclusion
   4. Background historical facts

4. True or False: A list of facts with no overall claim or recommendation is an argument.

Introduction

LSAT Logical Reasoning questions require rapid and precise analysis of short arguments. The first skill you must develop is the systematic deconstruction of each stimulus to expose its core reasoning—identifying the premises, the conclusion, and any parts that are merely background. Without this, detecting weaknesses or supporting evidence is almost impossible.

Being able to deconstruct and map out the structure of the argument is foundational, no matter which question type you encounter—whether it's to identify a flaw, strengthen, weaken, or find an assumption.

Key Term: argument
A group of statements, one of which (the conclusion) is claimed to follow from others (the premises), which provide support.

Recognising and parsing arguments lets you avoid traps set by irrelevant details, misplaced conclusions, or confusing wording.

Premises, Conclusions, and Facts

Every logical reasoning argument is built from statements that serve specific roles:

• Premises: Statements providing support or reasons, usually accepted as true within the LSAT world.
• Conclusion: The main point the author wants you to accept.
• Background facts: Statements that provide context but do not directly support the conclusion.

Key Term: premise
A statement intended to offer support or evidence for the conclusion.

Key Term: conclusion
The main claim or point the argument seeks to establish.

A core LSAT skill is to find the conclusion even when it is not the last (or even first) sentence, and to distinguish it from premises or contextual background.

Common Indicators

While not always present, certain words help identify a statement's function.

• Premise indicators: because, since, as, for, given that, after all
• Conclusion indicators: therefore, thus, hence, so, it follows that, consequently

Key Term: indicator
A word or phrase that signals the presence of a premise or conclusion within an argument.

Worked Example 1.1

Stimulus:
"Air pollution has fallen in the city since 2010, largely because of stricter regulations. Therefore, if these regulations are maintained, the city’s air quality will continue to improve."

Question: Identify the premise and the conclusion.

Answer:
Premise: "Air pollution has fallen in the city since 2010, largely because of stricter regulations."
Conclusion: "If these regulations are maintained, the city’s air quality will continue to improve."

Distinguishing Arguments from Fact Sets

Not every LSAT stimulus is an argument. Many just present facts (known as 'fact sets'), which lack a main point to be proved.

If a passage simply lists data, stats, or events without recommending, interpreting, or predicting anything, it's not an argument.

Key Term: fact set
A stimulus in which information is provided with no claim that one statement follows logically from others.

Worked Example 1.2

Stimulus:
"There are four major rivers in the country. Over the past year, rainfall has increased by 30%. The price of agricultural land has also risen."

Question: Is this passage an argument? Why or why not?

Answer:
No. There is no overall claim or main point linking these facts. This is a fact set, not an argument.

Identifying Assumptions

Often, an LSAT argument needs an unstated connection to get from premises to the conclusion. This missing link is the 'assumption'.

Key Term: assumption
An unstated but necessary idea that connects the premises to the conclusion—without it, the argument won’t hold.

Key Term: necessary assumption
A statement that must be true for the argument to work.

Worked Example 1.3

Stimulus:
"All energy-efficient cars are eligible for tax credits. Gina’s car is eligible for a tax credit. Therefore, Gina’s car is energy-efficient."

Question: What assumption is present? What is the flaw?

Answer:
The argument assumes that only energy-efficient cars can receive tax credits. But the premise only says all energy-efficient cars get credits, not that no other car can. The flaw is confusion of sufficient and necessary conditions.

How to Systematically Deconstruct

Apply a consistent approach every time:

1. Read for argument structure: Ask, "Is there a main claim? If so, what statements support it?"
2. Use indicator words cautiously: They help but are not foolproof.
3. Check for background information: Not all statements play a logical role.
4. Test potential assumptions: Consider what would make the conclusion not follow from the premises.
5. Diagram if conditional statements are present: Write $A \rightarrow B$ if "If A, then B" is used.

Revision Tip

When unsure, rephrase the passage in your own words and pinpoint what the author wants you to believe most—this is usually the conclusion.

Multiple Conclusions and Nested Claims

Sometimes a stimulus includes intermediate conclusions (claims supported by premises that, in turn, support a further conclusion).

Key Term: intermediate conclusion
A statement serving as both a conclusion (from the premises before it) and a premise (for the final conclusion).

Worked Example 1.4

Stimulus:
"Research shows regular exercise improves memory. Therefore, to succeed academically, students should exercise regularly, as strong memory is essential for good academic performance."

Question: Identify any intermediate conclusions.

Answer:
Intermediate conclusion: "Regular exercise improves memory."
Final conclusion: "To succeed academically, students should exercise regularly."

Separating Irrelevant Information

The LSAT often includes irrelevant facts to confuse you. Focus only on statements supporting or contradicting the conclusion.

Exam Warning

Do not simply pick the last sentence as the conclusion—LSAT writers mix up order to test your reasoning.

Spotting Flaws While Deconstructing

To prepare for reasoning questions, look for:

• Unwarranted leaps from premises to conclusion
• Confusion between correlation and causation
• Generalizations without support

Key Term: flaw
An error or weakness in the logic linking premises to conclusion.

Worked Example 1.5

Stimulus:
"A recent poll shows that 75% of residents favour new public transport lines. Therefore, the city council should immediately approve the project."

Question: Identify one possible flaw.

Answer:
The argument assumes that majority opinion is sufficient justification for taking action immediately. It ignores potential practical or budgetary obstacles.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Deconstruction of LSAT stimuli involves identifying premises, the conclusion, and background information
• Premises usually provide evidence; conclusions state the main claim
• Some stimuli are fact sets, not arguments; do not invent links
• Assumptions are the hidden connections making arguments work
• Indicator words ('because', 'therefore') help but are not always present or reliable; always test structure actively
• Common argument flaws include unwarranted assumptions, generalizations, or confusing correlation and causation

Key Terms and Concepts

• argument
• premise
• conclusion
• indicator
• fact set
• assumption
• necessary assumption
• intermediate conclusion
• flaw