Doing so is not unsound, but it may prevent us from finding a refutation when one exists. Each time you resolve two clauses, rename any free variables that are left over in the resulting clause. Within a clause, variables must be renamed uniformly. Relational Resolution with Free Variables Take this example. Everyone loves and respects clowns.
All logicians are clowns.
Show that everyone loves and respects logicians. First thing to do is translate the sentences into relational logic. Everyone loves and respects clowns. All logicians are clowns. Everyone loves and respects logicians.