We use the rules to reduce a sequent to a conjunction of simple sequents, sequents that only mentions propositional letters, with no connectives, and no repetitions — in this example, we find a single simple sequent, equivalent to our starting sequent in the sense that both are valid in the same universes. This shows our starting sequent is not a tautology. It is simple to provide a counterexample to a simple sequent, and this provides a counter-example to the strtting sequent.