A full appreciation, in contemporary terms, of the importance of Marie Jaëll (1846-1925) to the understanding and propagation of Liszt’s piano technique requires a vigorous re-examination of the complex personality of this pianist, composer, teacher, writer, and friend of Liszt. Because of her own ability to capture the magic of Liszt’s playing, Marie Jaëll wanted to transmit this pianistic miracle and the way of teaching it to generations to come. For this reason the pedagogical side of her personality has taken on more and more importance as time has gone by. Accepting as a personal crusade the proving of the essential integrity and the artistic truth of Lisztian technique, in her work she called on the scientific methods and analyses of Positivism in her work. Her approach can sometimes be obscure, especially for those who find themselves in more pragmatic times. The purpose of this article is therefore to distinguish between the essential and the secondary in the writings of Marie Jaëll so as to better understand and appreciate the exceptional revelations that she offers.