That thing is called....

Imagine, for a moment, that you are perched on the edge of a small wooden platform, 40 metres above the ground, with nothing to hold on to except a small length of wood attached to the ceiling of a large tent by two long pieces of rope. Now, imagine yourself leaping from the board, clinging tightly to the trapeze with sweaty, slippery fingers as you sweep a tight stomach-crushing arc through the air.

You are just about to reach the top of your swing, and are considering letting go of the trapeze, to somersault gracefully through the air, and be caught one-handed by a man hanging by his knees from another trapeze, who you're rather hoping has turned up while you were turning blindly in the air.

There is only one thing that could convince your otherwise sane mind that everything will be alright, and that you'll beat the odds and end up on the platform at the other side of the tent, to tumultuous audience applause. That thing is called trust.

You have no idea, as you let go of your trapeze, whether your partner has timed his swing correctly, or has enough height to reach you, or is not going to lose concentration because he's just remembered that he's forgotten to clean out the llamas that morning. You just have to trust him that he will do his half of the job properly.

Without trust, the stunt could not possibly work - either party would consider the odds of messing things up; and immediately start the long climb down the ladder to the ground, shaking their heads at the very idea.

As an even more spectacular stunt, it's been alleged that faith - a close relative of trust, but with poorer sight - can actually move mountains. Circus impressarios have not, however, been able to confirm this allegation, circuses being uncommon in mountainous areas.