LSAT Logical Reasoning Foundations Course
Five lessons that build LSAT Logical Reasoning skills: finding conclusions, identifying assumptions, strengthening and weakening arguments, recognizing flaws, and handling inferences, principles, roles, and paradoxes.
What you will learn
- Find the conclusion and map how premises support it.
- Identify necessary assumptions with the negation test.
- Strengthen and weaken arguments using evidence quality.
- Recognize common logical flaws and explain paradoxes.
- Apply inference, principle, and role skills under timed conditions.
Before you start
- Basic English reading ability.
- Familiarity with everyday arguments and debates.
- About 75 minutes of study plus regular practice.
Lesson 1 Finding the Conclusion and Argument Structure
LSAT Logical Reasoning rewards readers who can locate the conclusion and see how premises support it. Start by asking what the author is trying to prove; conclusion indicators such as therefore, thus, and consequently often mark it. Then identify the evidence, distinguish background information from support, and notice whether the argument relies on an unstated step. On test day, read the argument once, label the conclusion in your mind, and use the question stem to decide what you must find.
Indicator drill: conclusion indicators (therefore, thus, consequently, so) and premise indicators (because, since, given that) tell you where to look. After finding the conclusion, read the argument again and ask whether each sentence supports it or provides context.
Example
Therefore marks the conclusion: The library is underfunded, so it cannot serve the community. The first clause is evidence; the second is the conclusion.
Worked example: "The survey is reliable; therefore, the product will sell well."
The conclusion is the product will sell well; the survey is the premise that must be evaluated.
Lesson 2 Identifying Necessary Assumptions
Necessary assumptions are unstated claims an argument needs in order to work. A useful test is the negation test: if the assumption were false, would the reasoning collapse? Look for gaps between evidence and conclusion, such as assuming a sample represents the whole group or that a comparison is fair. When answer choices present assumptions, reject ones that are too strong or merely compatible with the argument. The correct answer is usually the essential bridge the author must accept.
Negation practice: for a candidate assumption, negate it and see whether the argument collapses. If the argument still works, the assumption is not necessary; if it breaks, the assumption is required.
Example
Assumption: Higher-paid workers are more productive. Negation: Pay and productivity are unrelated, which removes the link between salary and output.
Worked example: Argument: "Most students improved after the new course, so the course caused the improvement."
Necessary assumption: students who took the course would not have improved without it.
Lesson 3 Strengthen, Weaken and Evidence Evaluation
Strengthen and weaken questions ask how new information affects an argument. The best answer either adds support to a weak link or introduces an alternative explanation that undercuts the conclusion. Watch for evidence quality: a small sample, a biased comparison, or an uncontrolled experiment weakens claims, while replication, random assignment, and relevant comparisons strengthen them. Read the stem carefully because strengthen and weaken questions look similar but require opposite work.
Link test: identify the weakest link between evidence and conclusion, then choose the option that directly affects that link. For weaken questions, an alternative explanation or a flaw in the sample usually works best.
Example
Weaken: The city lowered speed limits at the same time, so the drop in accidents may not come from bike lanes. Strengthen: A second city with bike lanes and no other changes saw the same drop.
Worked example: Claim: "Dogs at this shelter are healthy because they all passed a checkup."
Weak link: the checkup may miss hidden diseases, so a result that found hidden disease in some dogs would weaken the claim.
Lesson 4 Common Flaws and Paradox Explanations
LSAT flaw questions ask you to name or describe a defect in an argument. Review the recurring patterns: confusing necessary and sufficient conditions, treating correlation as causation, generalizing from a small sample, false dilemmas, circular reasoning, and attacking the person. For paradox questions, find an answer that explains both facts without denying either one. The correct choice often introduces a new piece of information that makes the surprising result consistent.
Flaw pattern matching: build a list of flaws with examples: correlation/causation, small sample, false dilemma, necessary/sufficient confusion, and ad hominem. In paradox questions, choose the answer that explains both facts without denying either.
Example
Flaw: Three friendly applicants do not prove the next applicant will be friendly. Paradox: Revenue rose because returning customers bought more books even though foot traffic fell.
Worked example: "Ice cream sales and drownings rise together, so ice cream causes drowning."
The flaw is treating correlation as causation; warm weather is a common cause.
Lesson 5 Inferences, Principles, Roles and Test Strategy
Inference questions ask what must be true or most strongly supported; do not import outside knowledge or overstate the text. Principle questions match a rule to a situation, while role questions ask how a sentence functions. Manage time by doing the fastest questions first, pre-phrasing answers, and eliminating choices that are too strong or outside the passage. After each practice set, review explanations in batches so patterns become automatic.
Must-be-true test: if a statement could be false while the passage stays true, it is not a valid inference. Keep answers within the text, avoid new examples, and choose the most supported option even if it sounds surprising.
Example
Inference: Some remote employees have passed the background check. Role: The limited charging infrastructure is a consideration against electric buses.
Worked example: Passage says "All applicants must submit a resume."
Valid inference: anyone hired from this process submitted a resume. Not valid: all resumes are short.