This dissertation investigates the thought and the musical and artistic aesthetic of the French-American composer Dane Rudhyar (1895-1985). Seeking justification for his views and aesthetic in a variety of areas and distrusting both rationalism and mysticism exclusively in their own terms, Rudhyar chose an eclectic path. The qualities in his musical, visual, literary, philosophical and astrological work come not just from certain late nineteenth-century and early twentieth-century French and German sources, but also from the Orient (particularly India and Japan), and from the early idealism and optimism of the New World. The multi-faceted nature of his work and life also reflects his philosophy of Wholeness, i. e. the dynamic interplay between Multiplicity and Unity. During my research, I have undertaken the tasks of gathering together the hugely disparate body of Rudhyar's (philosophical, musical, visual, astrological and literary) works, and of investigating what stands behind his vision. While the content of this study is not intended to follow any chronological order, the principal views of Rudhyar have often affected the general flow and layout of the dissertation, which is structured in three large parts. The first deals with Rudhyar's European background and his `seed' philosophy. The second is an examination of Rudhyar's fascination with the Orient and its conceptual ramifications. The third evaluates Rudhyar's American identity against the background of some of the social and cultural overtones that shaped the United States, particularly up until World War II. In the musical discussions of this dissertation, emphasis has been placed on his piano music; works examined include Transmutation, Three Early Pieces, Theurgy and Three Melodies (for flute with piano and cello accompaniment). These analytical sections will be presented in the first and second parts and are not intended to be comprehensive accounts of the compositions in question but merely illustrations of the relationship between idea and realisation