|Necessity, philosophy: different kinds of necessity are distinguished, differing in their strength. For example, physical, logical or metaphysical necessity. See also necessity de dicto, necessity de re.|
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Necessary/Wessel: often: "~ p > p" interpreted as necessary - Problem: no way to differentiate between "p" and "p is necessary" - "logically impossible": "p> ~ p": then "~ p" and "p is impossible" equivalent.
Necessity/Wessel: when I designate a sentence as needed, I give a hint about my judgment reasons - possibility: Speaker abstains from judgment.
Logical/physically necessary/Wessel: 1. what is logically necessary is also factually necessary - 2. What is factually possible is also logically possible - 3. What is factually not necessary, is also not logically necessary - 4. what is logically impossible , is also factually impossible - logical modality sets limits on the factual modality - because logical modality alone from linguistic requirements, not ontologically - logical truth is equivalent to logical demonstrability and logical necessity - logical falsifiability is equivalent to logical falsehood and logical impossibility.
Logik Berlin 1999