The Higher Self is a concept introduced by Roberto Assagioli, the founder of psychosynthesis, into transpersonal psychology. This notion is explained and linked up with the Western mystical tradition. Here, coming from antiquity and specifically from the neo-Platonic tradition, a similiar concept has been developed which became known as the spark of the soul, or summit of the mind. This history is sketched and the meaning of the term illustrated. During the middle ages it was developed into a psychology of (...) mysticism by Thomas Gallus, popularized by Bonaventure, and radicalized by the Carthusian writer Hugh of Balma. Spark of the soul signifies an "organ of the mystical experience." It is argued that the split introduced into history between outer and inner experience has lain dormant ever since the 13th century, with inner experience relegated to the private and mystical realm. By introducing this concept, transpersonal psychology reconnects with this tradition and has to be aware of the legacy: to achieve the theoretical, and if possible scientific, integration of both types of experience by drawing on the experiential nature of this concept and fostering good research. (shrink)