Critical Reasoning: Logical Flaws, Assumptions, and Argument Analysis

Must Be True

Find the answer that must follow from the text. Avoid 'could be true' or 'new information.'

Main Point

Identify the author's ultimate conclusion. Beware of 'intermediate conclusions.'

Flaw in Reasoning

Describe the logical error. Ask: 'Why do the premises fail to prove this specific conclusion?'

Strengthen

Find a piece of new information that makes the conclusion more likely to be true.

Weaken

Find a piece of new information that attacks the assumption or provides an alternative explanation.

Sufficient Assumption

Find the 'missing link' that, if true, makes the argument 100% logically valid.

Necessary Assumption

Identify a requirement that must be true for the argument to even stand. (Use the Negation Test).

Parallel Reasoning

Match the logical structure of the stimulus, not the topic. Look for matching 'logical force.'

Resolve the Paradox

Find the answer that explains how two seemingly contradictory facts can both be true.

Conclusion Indicators

Thus, therefore, hence, so, clearly, consequently, as a result.

Premise Indicators

Because, since, for, after all, given that, in that.

Sufficient Indicators

If, when, whenever, every, any, each, people who.

Necessary Indicators

Then, only, only if, must, required, unless, until, without.

Contrapositive

Flip the terms and negate both. (A to B becomes NOT B to NOT A). This is the only valid deduction.

Mistaken Reversal

The error of thinking B to A is true just because A to B is true.

Mistaken Negation

The error of thinking NOT A to NOT B is true just because A to B is true.

The 'Unless' Rule

'A unless B' means NOT A to B (Negate the first part, it becomes the 'if' part).

Some (Quantifier)

At least one (1-100%).

Most (Quantifier)

More than half (51-100%).

Correlation vs. Causation

Assuming that because two things happen together, one caused the other.

Ad Hominem

Attacking the person making the argument rather than the logic of the argument itself.

Straw Man

Misrepresenting an opponent's position to make it easier to attack.

Circular Reasoning

The conclusion is just a restatement of one of the premises.

Hasty Generalization

Drawing a broad conclusion based on a very small or unrepresentative sample.

False Dichotomy

Assuming only two options exist when there could be more.

Equivocation

Using the same word with two different meanings within one argument.