 Let \(P\), for example, be a primitive one-place predicate. Then if the semantics is negative, \(Pt \rightarrow \rE!t\) is valid. But now consider the substitution instance \({\sim}Pt \rightarrow \rE!t\), in which the open formula \({\sim}Px\) is substituted for \(P\). This substitution instance is false when \(t\) is empty. Hence valid formulas may have invalid substitution instances. The same holds for ordinary neutral semantics that make conditionals true whenever their consequents are true.