A tall, striking doctor with an unusually piercing gaze sits opposite his patient, firmly pressing her knees between his own. He stares fixedly into the patient’s eyes, stroking her limbs, and then passing his hands in front of her body in a series of cryptic motions. Is this man a hypnotist or a movie villain? A healer or a charlatan? In the case of Franz Anton Mesmer, the answer to all of the above could be yes.

Mesmer was an 18th century doctor who developed the theory of animal magnetism (more about that later), as well as a related style of treatment that came to be known as mesmerism. His theories were debunked in his time and sound bizarre today, but some credit him with laying the foundation for the practice of modern hypnotism. He is also part of the select group of people in history to have an entire verb—mesmerize—named for him.