Tableaux methods offer elegance, flexibility and analytic proof theory for a wide variety of logics.
Some theorem provers based on tableaux like HARP are very sophisticated while others as 3TAP offer a great flexibility. Isabelle is a generic, interactive theorem prover based upon a form of resolution. This will be demonstrated on examples, using the Partial Predicate Logic. In the second part we will discuss the Classical Reasoner. Because of the correspondance between natural deduction and sequent calculus, the tableau method is addapted to a natural deduction style, which seems easier to automate.