Introduction to logical reasoning - Identifying premises, co...

Learning Outcomes

By the end of this article, you will be able to clearly distinguish between premises, conclusions, and assumptions in LSAT logical reasoning arguments. You will know how to identify these elements quickly using indicator words, evaluate their logical function, and spot hidden assumptions. These skills will allow you to break down LSAT arguments efficiently, apply appropriate techniques to various question types, and make sound answer selections on the exam.

LSAT Syllabus

For LSAT, you are required to understand how logical arguments are constructed and how to analyze their key elements. When preparing for questions in this topic, focus on the following:

• distinguishing between premises and conclusions in argument stimuli
• spotting key logical indicator words that signal premises or conclusions
• identifying both explicit and implicit (unstated) premises
• analyzing how premises are intended to support the conclusion
• detecting logical gaps and implicit assumptions
• applying these skills to LSAT question types, including Main Point, Assumption, and Flaw 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 of the following is a common premise indicator?
   1. thus
   2. since
   3. therefore
   4. in conclusion
2. Which statement is most accurate?
   1. Every argument has an assumption.
   2. Premises are always opinions.
   3. An assumption is often not stated directly.
   4. Conclusions must always be at the end of an argument.

3. What does an assumption do in an LSAT argument?

4. True or false? The word "because" usually introduces a conclusion.

Introduction

LSAT logical reasoning questions are built around arguments. On test day, your task is to dissect these arguments and distinguish clearly between their components: premises (reasons or evidence), conclusions (main claims), and assumptions (unstated beliefs connecting the two). Accurate identification of each is essential for success—these distinctions form the basis of numerous LSAT question types.

Recognizing the function and placement of each element can help you answer questions quickly and avoid falling for trap answers. The distinction is subtle but absolutely critical for efficient LSAT analysis.

Key Term: argument
An argument is a group of statements, including one intended as the main claim (conclusion) and others offered in support (premises).

Premises

A premise is a statement given as a reason in support of the argument’s main claim. On the LSAT, premises may be facts, data, examples, or principles—anything the author expects you to accept as true within the argument’s world.

Key Term: premise
A statement presented as evidence or support for the conclusion of an argument.

Typical premise indicators include words such as “because,” “since,” “given that,” “for,” “as,” and “due to.” These words usually signal that the following material is being offered as support.

Worked Example 1.1

Argument: “Regular exercise increases memory retention. Kate exercises daily. Therefore, Kate is likely to have good memory retention.”

Question: What are the premises in this argument?

Answer:
The premises are “Regular exercise increases memory retention” and “Kate exercises daily.” These sentences provide the evidence used to justify the conclusion.

Revision Tip (Premises)

Underline statements following “because,” “since,” or “given that”—they are likely premises.

Conclusions

A conclusion is the statement the author wants you to accept as true, based on the premises provided. Every LSAT argument is structured to lead to a single main claim.

Key Term: conclusion
The central claim the author aims to establish using the provided premises.

Common conclusion indicators include “therefore,” “thus,” “consequently,” “so,” “it follows that,” and “as a result.” Remember, not all conclusions are signposted. If in doubt, ask: “What is the author trying to prove?”

Worked Example 1.2

Argument: “All successful applicants submit their forms early. Jordan submitted his application early. Thus, Jordan is a successful applicant.”

Question: Which part is the conclusion?

Answer:
The conclusion is “Jordan is a successful applicant.” The preceding statements merely supply reasons to support this claim.

Revision Tip (Conclusions)

Try the “Why Test”: pick a statement and ask “Why?” If the rest of the argument answers the question, the statement is the conclusion.

Assumptions

An assumption in LSAT arguments is any statement that connects the premises to the conclusion but is left unstated. Assumptions act as bridges, filling in the logic the author takes for granted.

Key Term: assumption
An unstated belief or idea required for the conclusion to logically follow from the premises.

There are two types of assumption questions commonly tested:

Key Term: necessary assumption
An assumption that must be true for the conclusion to be valid. If false, the argument fails.

Key Term: sufficient assumption
An assumption that, if true, is strong enough by itself to guarantee the conclusion (even if it is stronger than the argument demands).

Spotting the assumption involves identifying any “missing” step between the stated evidence and the claim.

Worked Example 1.3

Argument: “All high scorers use time management strategies. Maya scored highly. Therefore, Maya must have used time management strategies.”

Question: What is the hidden assumption in this argument?

Answer:
The author assumes that no high scorers fail to use time management strategies—that the link holds without exception. This is a necessary assumption because, if it’s false, the conclusion is unsupported.

Revision Tip (Assumptions)

For necessary assumption questions, apply the “Negation Test”: If denying the assumption destroys the argument, it is necessary.

Exam Warning

Necessary assumptions and sufficient assumptions are not the same. A necessary assumption is required for the argument to make sense. A sufficient assumption, if true, forces the conclusion to follow even if it adds information not present in the original argument.

Distinctions—Premises vs Conclusions vs Assumptions

A quick summary:

• Premises supply reasons or evidence.
• Conclusions are what the argument seeks to establish.
• Assumptions are unstated yet essential links between the two.

Worked Example 1.4

Argument: “To receive a scholarship, a student must have strong grades. Noah has strong grades. Therefore, Noah received a scholarship.”

Question: What is the flaw in this reasoning?

Answer:
The argument mistakes a necessary condition (“must have strong grades”) for a sufficient one, assuming that having strong grades alone guarantees the scholarship. The assumption is that strong grades are enough, which is not justified.

Why These Skills Matter

The LSAT directly assesses your ability to break arguments apart:

• Main Point questions require you to identify the argument’s conclusion.
• Assumption questions test your precision in spotting hidden logical bridges.
• Flaw questions demand awareness of when conclusions are not fully supported by the provided premises.

Quick, accurate analysis of premises, conclusions, and assumptions allows you to zero in on correct answers and dismiss tempting distractors.

Worked Example 1.5

Argument: “Every top-ranking law school prefers applicants with extensive voluntary work. Liam has volunteered at many organizations. Thus, Liam will be accepted to a top-ranking law school.”

Question: What misleading assumption does this argument rely on?

Answer:
The argument assumes volunteering is a sufficient condition for admission, not just a preferred quality. This gap between premise and conclusion is a logical flaw often tested on the LSAT.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• A premise is a statement of evidence or support for a conclusion
• A conclusion is the main claim, supported by premises
• Logical indicators help identify premises and conclusions, but are not always present
• Assumptions fill the gap between premises and conclusion—they are required or sufficient for the logic to work
• Necessary assumptions are required for the validity of the argument; sufficient assumptions, if true, guarantee the conclusion
• Careful identification of premises, conclusions, and assumptions is required for LSAT Main Point, Assumption, and Flaw questions

Key Terms and Concepts

• argument
• premise
• conclusion
• assumption
• necessary assumption
• sufficient assumption