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  "body": "\n## Summary\n\nA formula is satisfiable when some interpretation makes it true.\nIn [[propositional logic|09K9MWD2QQ]] an interpretation is an assignment of truth values to the variables.\nIn [[predicate logic|086QKPF0A6]] it is a [[structure|983GZBQYT4]] with an assignment of its elements to the free variables.\nSatisfiability is dual to validity: a formula is valid exactly when its negation is not satisfiable.\n\n## Explanations\n\n### L1 human\n\nA formula is satisfiable when it is possible to make it true.\nFor example, $p \\land \\neg q$ is satisfiable: take $p$ true and $q$ false.\nThe formula $p \\land \\neg p$ is not satisfiable, since $p$ cannot be true and false at once.\nDeciding satisfiability of propositional formulas is the SAT problem, a central problem of computer science.\n",
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