  We generalize several propositional preprocessing techniques to higher-order
logic, building on existing first-order generalizations. These techniques
eliminate literals, clauses, or predicate symbols from the problem, with the
aim of making it more amenable to automatic proof search. We also introduce a
new technique, which we call quasipure literal elimination, that strictly
subsumes pure literal elimination. The new techniques are implemented in the
Zipperposition theorem prover. Our evaluation shows that they sometimes help
prove problems originating from Isabelle formalizations and the TPTP library.
