Stage 35 · Logic & Quantifiers
35.2.3 Necessary and Sufficient Condition
35.2 Sufficient, Necessary, and Both
Point 3 of 5
35.2.3 Necessary and Sufficient Condition
Core idea"Have it and you're set, lose it and you can't": p and q guarantee each other, p⇔q, fully equivalent.
Module goal. Capture the relationship between hypothesis and conclusion with "is it enough to have it, can you do without it" — and learn to identify all three kinds of conditions.