Necessary/sufficient distinction
SAT glossary · Course Foundations
Definition
Refuting an objection to a claim is not proving the claim; killing one alternative explanation leaves the field open to a third. Named by the book as one of the two or three most heavily tested logical relations on the section, and the engine of the claim–objection–removal micro-text.
Necessary/sufficient distinction in plain English
This distinguishes two things people often confuse: knocking down ONE objection or alternative explanation to a claim is NOT the same as actually PROVING that claim is true — because even after removing one competing explanation, there could still be some completely different, third explanation nobody's ruled out yet. This is called out as one of the two or three most heavily tested types of logical reasoning in this whole section, and it's the engine behind a common passage structure: someone makes a claim, someone raises an objection, and the objection gets removed — but removing that one objection still doesn't PROVE the original claim.
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