Independent tagged axiomatization
= Independent tagged axiomatization
In a conservative language extension, attach a fresh nullary predicate $P_i$ to the $i$th axiom $A_i$ and use a self-indexing copy of $P_i\wedge A_i$. The fresh tag makes each new axiom independent of all the others, while forgetting the tags recovers exactly the original-language consequences. The <Craig trick> makes the resulting axiom set decidable.