In part four of our Magic Theory Blog Series, we re-visit Liderc's thoughts on the perils of "over-proving,"  or "over-selling," and look at ways to avoid the trap of over-proving yourself to your participants.

Find the original forum thread here.

Avoid the "Overproving Trap"

Many magicians, from professionals to hobbyists, fall into the trap of over-selling/over-proving.

I mean, how many videos have you seen where the magician is constantly flicking and snapping cards? How many times have you heard, "completely fair, right?" repeated over and over?

Body Language and Consistency

Spectators are observant; especially if they are invested in you. They notice what you do and what you don't do. Body language is huge, in fact more so then words sometimes.

To tie in with our previous post about consistency, imagine, all that constant flicking of a single card and then you go to do a DL and you tense up and become static. All that "over-proving" before has worked against you.
The only time you should ever prove anything more then you have to is if they become suspicious and they will only become suspicious based on your body language.

Let them Touch it

Get all their senses involved (maybe not taste so much) in "proving" so that they prove things to themselves, and you don't have to prove it to them.
Identity by Richard Sanders is a good example:

You have a card with marks on it, you let the spectator rub it to make sure the marks don't come off (thus also proving a single card). You don't say, "I only have one card in me hand," you just let them rub it. Then you can transfer the marks to another card. In your participants' minds, they felt it, they rubbed it, and it was only one card.
The more you say "Fair Choice?" the more you try to hard-sell something, the more they put up their defenses, the more you keep repeating the same thing over, the more it gets them to focus on what you don't want them to focus on. They will start asking themselves, "Well, was that really fair?"  It will make the end result less then what it could be.
Actions sometimes, and most times, speak louder than words. Body language, consistency, and involving the participant's senses are important.

Note from V:

Indeed, these are great thoughts - keep in mind, you can't convince anybody of anything, they can only convince themselves of something. Thus, subtle convincers, such as letting your participants touch something, are more powerful than "hard sell" convincers. If you try to over-prove, like Liderc said, you risk putting your participants on the defensive, or giving them a reason to believe something is amiss.

P.S. If you are wondering about the photo, it is an image from the play, "Death of a Salesman."