Autosave: 2022-12-23 15:30:07
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@ -37,6 +37,7 @@ Cannot be consistently denied as there is no possibility of it being false. It i
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## Formal definition
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> A proposition P is truth-functionally indeterminate if and only if it is neither truth-functionally true or truth-functionally false.
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> should be avoided in arguments, they 'prove' everything whi
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```
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P
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@ -34,6 +34,6 @@ From this we can derive the following property of logical possibility:
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## Logical necessity
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A sentence is _logically necessary_ if it is true in every logically possible circumstance which is to say: true on every possible truth functional assignment. Necessity and [logical truth](/Logic/General_concepts/Logical_truth_and_falsity.md#logical-truth) are therefore synonyms: anything that is logically true (a tautology) is true by necessity (could not be otherwise.)
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A proposition is _logically necessary_ if it is true in every logically possible circumstance which is to say: true on every possible truth functional assignment. Necessity and [logical truth](/Logic/General_concepts/Logical_truth_and_falsity.md#logical-truth) are therefore synonyms: anything that is logically true (a tautology) is true by necessity (could not be otherwise.)
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Further, every logical truth is logically possible but not everything that is logically possible is logically true. It is possible that it is raining but this is not logically necessary - it could be otherwise, i.e not raining. However it is not possible that it could be both raining and not raining.
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@ -23,8 +23,8 @@ $$ \{ P \leftrightarrow Q, P \lor Q, P \land Q \} $$
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| F | T | F | T |
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| F | F | T | F |
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| $P$ | $Q$ | $(P \leftrightarrow Q) \land (P \lor Q)) \leftrightarrow (P \lor Q)$ |
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| --- | --- | -------------------------------------------------------------------- |
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| $P$ | $Q$ | $(P \leftrightarrow Q) \land (P \lor Q)) \leftrightarrow (P \land Q)$ |
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| --- | --- | --------------------------------------------------------------------- |
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| T | T | T |
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| T | F | T |
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| F | T | T |
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