Logical Deduction and Evaluating Arguments
Logical deduction and evaluating arguments
An argument has premises (the reasons given) and a conclusion (the claim being pushed). Your first move is to label them. Conclusion markers include therefore, so, thus, hence, it follows that; premise markers include because, since, given that, studies show. If nothing signals the conclusion, ask what the writer wants you to believe - usually the first or last sentence.
Then test the link. Assumptions are unstated premises needed for the conclusion to follow. The right answer is usually a necessary assumption, so negate it: if the argument collapses when the option is false, that option is the assumption. Strengthen/weaken questions ask which option makes the conclusion more or less likely - not which is true, and not which proves anything.
Recurring flaws: confusing correlation with cause; generalising from a small or biased sample; attacking the person rather than the argument; circular reasoning (the conclusion smuggled into a premise); false dilemma; confusing necessary with sufficient conditions; and ignoring an alternative explanation.
Quantifiers matter. Some, most and all are not interchangeable; an argument that works with 'some' may fail with 'all'. Percentages mislead when base rates are unstated.
Worked rule. A shop raises prices and revenue falls; the manager concludes demand is elastic. That holds only if nothing else changed - a competitor opening next door would weaken it. Ask what else could explain the observation.
Trap: an option that merely restates a premise. It adds no support and is never the answer to an assumption question.