بالضرورة أن لا يكون
It is necessary that it not be.
ليس بالضرورة أن يكون
It is not necessary that it be.
The first asserts necessary non-occurrence, while the second merely denies necessary occurrence. They are not equivalent. “This meeting need not occur” does not mean “this meeting must not occur.” The meeting could be possible but not necessary.
In modern notation, □¬P differs from ¬□P. The first necessitates the negation; the second denies the necessity of affirmation.
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Semantic Fallacies: Defects of Matter, Form, and Predication
بالضرورة أن لا يكون
It is necessary that it not be.
ليس بالضرورة أن يكون
It is not necessary that it be.
The first asserts necessary non-occurrence, while the second merely denies necessary occurrence. They are not equivalent. “This meeting need not occur” does not mean “this meeting must not occur.” The meeting could be possible but not necessary.
In modern notation, □¬P differs from ¬□P. The first necessitates the negation; the second denies the necessity of affirmation.