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I'm Philip Ball, and in Discovery from the BBC, I'll be telling another story from the

history of science. It is Paris in 1784 and something revolutionary is on trial.

A German doctor named Franz Anton Mesmer is suspected of fraud. He claims to heal patients with what he calls animal magnetism.

Is he a quack, a charlatan, or a visionary? The French government has appointed a committee of experts to investigate.

It includes two of the most renowned experimental scientists of their age,

the American inventor Benjamin Franklin, and the French

chemist Antoine Lavoisier who himself faced trial leading to a death sentence in the French

revolution ten years later.

The official inquiry in Tamesma's methods was one of the first times that what we might

now call paracycology, a claim to achieve physical effects with the power of

the mind, came under close scientific scrutiny.

It's tempting to see it as a battle of reason against superstition.

But with placebo effects, hypnotism and talking cures for psychological disturbances,

all now offering evidence of how the mind

really can affect the body. That's too simplistic a story. Besides, nothing Mesmo was

claiming was outrageous for its time.

The challenge for La Voisier and Franklin was no different from the one we still face today.

How reliably can we know what the mind is capable of?

Mesmer was born in 1734

...