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A logical principle that rejects the classical law of excluded middle (either a proposition is true or its negation is true). Instead, the law of the included third allows for a third truth-value: a proposition can be both true and false, or neither, or somewhere in between. It is foundational for paraconsistent logic, fuzzy logic, and dialectical thinking, where contradictions are not automatically fatal but can be integrated into reasoning. In complex systems—such as social contradictions, quantum superpositions, or borderline cases—a strict true/false binary fails; the included third acknowledges that reality often contains overlapping, ambiguous, or transitional states.
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