Mesmer was known for his theory of "animal magnetism," which he believed was a universal force that could be used to heal illnesses. He developed a technique called "mesmerism" that involved using magnets and passes to manipulate this force.
While Mesmer's theories were later discredited, his name and techniques became associated with the phenomenon of hypnotism. The word "mesmerize" entered the English language in the late 18th century, reflecting the impact of Mesmer's ideas and practices.