2022-04-23 13:26:53 +01:00
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---
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2024-06-16 18:15:03 +01:00
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tags:
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- propositional-logic
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- logic
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2022-04-23 13:26:53 +01:00
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---
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2022-12-25 15:00:05 +00:00
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# Disjunction Introduction
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2024-02-02 15:58:13 +00:00
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This rule can seem a little odd: like we are randomly introducing an additional
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proposition without giving any justification. However this is just a consequence
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of the fact if $P$ is true, so is $P \lor Q$ since disjunction is not the same
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as conjunction: only one disjunct needs to be true for the compound disjunction
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to be true. This is represented in the context of
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[truth-trees](Truth-trees.md#disjunction-decomposition) by the fact that truth
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can pass up via either branch of a disjunction pattern. This rule is sometimes
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also referred to (confusingly) as _Addition_.
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2022-04-23 13:26:53 +01:00
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2024-02-16 16:14:01 +00:00
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