We give a syntactic translation from first-order intuitionistic predicate logic
into second-order intuitionistic propositional logic IPC2. The translation
covers the full set of logical connectives ∧, ∨,
→, ⊥, ∀, and ∃, extending our
previous work, which studied the significantly simpler case of the
universal-implicational fragment of predicate logic. As corollaries of our
approach, we obtain simple proofs of nondefinability of ∃ from the
propositional connectives and nondefinability of ∀ from ∃
in the second-order intuitionistic propositional logic. We also show that the
∀-free fragment of IPC2 is undecidable.