LSAT—India Logical Reasoning: Argument Analysis Syllabus

What does an Evaluate the Argument question ask?

To identify the question, test, or piece of information whose answer would most help determine whether the argument is strong or weak (i.e., it is relevant to the argument's key assumption).

What is the Variance Test for Evaluate questions?

For each answer, consider the two extreme answers to the proposed question. If one extreme strengthens and the other weakens the argument, that choice is relevant and correct. If the argument is unaffected either way, it is wrong.

Name three common causal reasoning flaws.

(1) Correlation mistaken for causation, (2) reversed causation (cause and effect swapped), (3) ignoring a third/common cause or coincidence that explains the correlation.

How do you weaken a causal argument (cause X produces effect Y)?

Show an alternative cause for Y, show Y occurring without X, show X occurring without Y, reverse the causal direction, or show the correlation is coincidental.

How do you strengthen a causal argument?

Rule out alternative causes, show that when the cause is present the effect follows, show that absence of the cause means absence of the effect, or eliminate reverse causation/coincidence.

What is the post hoc ergo propter hoc fallacy?

'After this, therefore because of this' — concluding that because event B followed event A, A caused B. It confuses temporal sequence with causation.

What is an unrepresentative (biased) sample flaw?

Drawing a conclusion about a whole population from a sample that does not accurately reflect it (too small, self-selected, or atypical), making the generalization unreliable.

What makes a sample valid for a generalization?

It must be sufficiently large and representative (randomly or proportionally drawn) of the target population so its characteristics can be reasonably extrapolated.

What is the difference between percentages and absolute numbers as a statistical flaw?

Confusing a change in percentage/rate with a change in actual quantity. A higher percentage of a smaller total can mean fewer in number, and vice versa; arguments that conflate the two are flawed.

What is a formal logical fallacy?

An error in the structure/form of a deductive argument, where the conclusion does not follow from the premises regardless of content (e.g., affirming the consequent, denying the antecedent).

What is the fallacy of affirming the consequent?

From 'If P then Q' and 'Q,' wrongly concluding 'P.' Q being true does not establish P, since other things could cause Q. (Invalid form.)

What is the fallacy of denying the antecedent?

From 'If P then Q' and 'not P,' wrongly concluding 'not Q.' P being false does not guarantee Q is false. (Invalid form.)

What is an informal fallacy?

An error in reasoning arising from the content, context, or language of an argument rather than its logical form (e.g., ad hominem, straw man, equivocation, appeal to authority).

What is the ad hominem fallacy?

Attacking the person making an argument (their character, motives, or circumstances) instead of addressing the argument itself.

What is the straw man fallacy?

Misrepresenting or distorting an opponent's position into a weaker version, then refuting that weaker version instead of the actual claim.

What is the equivocation fallacy?

Using a single word or phrase in two different senses within the same argument, making the reasoning appear valid when it is not.

What is circular reasoning (begging the question)?

An argument whose conclusion is assumed within its own premises, so the premise and conclusion essentially restate the same claim and prove nothing new.

What is the false dichotomy (either/or) fallacy?

Presenting only two options as if they were the only possibilities when other alternatives exist, then forcing a conclusion by eliminating one.

What is the part-to-whole (composition) fallacy?

Assuming that what is true of the parts must be true of the whole (composition), or that what is true of the whole must be true of each part (division).

What is the strategy for Identify the Flaw questions?

Pinpoint exactly why the conclusion does not follow from the premises, then match that gap to a flaw answer choice. Pre-phrase the error before reading choices and watch for common named fallacies.

In Flaw questions, what trap do abstract answer choices set?

They describe a flaw the argument did NOT commit. The choice must describe an error the argument actually makes; tempting answers name real fallacies that are absent from the stimulus.

How do you symbolize a conditional statement 'If A then B'?

A → B, where A is the sufficient condition (trigger) and B is the necessary condition (result). A guarantees B; B is required for A.

What is the difference between sufficient and necessary conditions?

A sufficient condition is enough to guarantee the result (the trigger). A necessary condition is required for the result to occur (without it, the result cannot happen). In A→B, A is sufficient, B is necessary.

Which words typically introduce the sufficient condition?

If, when, whenever, all, every, any, in order to, people who. These mark the trigger that goes on the left of the arrow.

Which words typically introduce the necessary condition?

Then, only, only if, must, requires, depends on, necessary. These mark what is required and go on the right of the arrow.

What is the contrapositive of A → B, and is it logically equivalent?

The contrapositive is not-B → not-A. Yes, it is logically equivalent to the original and always true when the original is true. (Reverse and negate both terms.)

How do you form a contrapositive correctly?

Reverse the order of the two terms AND negate each of them. For A → B: swap to B...A and negate both, giving not-B → not-A.

What does 'only if' indicate, and how is 'A only if B' diagrammed?

'Only if' introduces the necessary condition. 'A only if B' is diagrammed A → B (A is sufficient, B is necessary).

What is the logical relationship between 'All A are B' and 'Some B are A'?

'All A are B' validly yields 'Some B are A' (assuming A exists). However, 'All A are B' does NOT yield 'All B are A' — the converse is not guaranteed.

What can and cannot be inferred from 'Most A are B' combined with 'Most A are C'?

You can infer that at least some A are both B and C (since two majorities of the same group must overlap). You cannot infer anything about most B, most C, or any relationship outside A.

How do 'some' and 'all/none' relate as quantifiers?

'Some' means at least one (and is compatible with all). The negation of 'all A are B' is 'some A are not B'; the negation of 'no A are B' (none) is 'some A are B.' 'Some' statements are reversible: 'some A are B' = 'some B are A.'