Free vs. Bound Variables
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State
A variable is bound when a quantifier's scope covers it, free otherwise. Statements have no free variables.
Show
In (x)Fx ⊃ Gx, the second x is free — the quantifier's scope ended at Fx. Compare (x)(Fx ⊃ Gx).
Watch for
Parentheses set quantifier scope exactly as they set connective scope (129). Same discipline, higher stakes.
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Unlocks
- Nothing yet depends on this.