F. Matthias Alexander was an Australian actor, author and educator, who is best known as the inventor of Alexander Technique, a method for "unlearning" acquired habits of movement and posture that are harmful or suboptimal, and allowing natural, healthy patterns of body use to emerge in their place. Alexander Technique is now taught by specially trained instructors through in-person lessons around the world, and is particularly popular among musicians and other performance artists. In this 1923 book, considered by many to be his best, Alexander explains the principles of his technique and the theory behind it. It includes an introduction by the American philosopher and educator John Dewey, who studied the technique with Alexander.