OBSERVATION

Some things, such as continuity at a point, are best learned via exercises in their negation, because that way the student is having to deal only with a ‘solid’ statement at the beginning, instead of a ‘fluid’ statement. (This concept of access via negation is reminiscent of the probability formula P(A) = 1 – P(S – A), and is a form of bankshot.)
keywords:
[logic]
[logical quantification]
[mathematics]