theorem prover and countermodel generator

 This package provides the Prover9 resolution/paramodulation theorem
 prover and the Mace4 countermodel generator.
 .
 Prover9 is an automated theorem prover for first-order and equational
 logic. It is a successor of the Otter prover. Prover9 uses the
 inference techniques of ordered resolution and paramodulation with
 literal selection.
 .
 The program Mace4 searches for finite structures satisfying first-order
 and equational statements, the same kind of statement that Prover9
 accepts. If the statement is the denial of some conjecture, any
 structures found by Mace4 are counterexamples to the conjecture.
 .
 Mace4 can be a valuable complement to Prover9, looking for
 counterexamples before (or at the same time as) using Prover9 to search
 for a proof. It can also be used to help debug input clauses and formulas
 for Prover9.