Traditionally, magicians refuse to reveal the methods behind their tricks to the audience. Membership in professional magicians' organizations often requires a commitment never to reveal the secrets of magic to non-magicians. The teaching of performance magic was once a secretive practice.[citation needed] Magic performances tend to fall into a few specialties or genres. Stage illusions use large-scale props and even large animals. Platform magic is performed for a medium to large audience. Close-up magic is performed with the audience close to the magician. Escapology involves escapes from confinement or restraints. Pickpocket magicians take audience members' wallets, belts, and ties. Mentalism creates the illusion that the magician can read minds. Comedy magic is the use of magic combined with stand-up comedy, an example being Penn & Teller. Some modern illusionists believe that it is unethical to give a performance that claims to be anything other than a clever and skillful deception. Others argue that they can claim that the effects are due to magic. These apparently irreconcilable differences of opinion have led to some conflicts among performers. Another issue is the use of deceptive practices for personal gain outside the venue of a magical performance. Examples include fraudulent mediums, con men and grifters who use deception for cheating at card games.