I became interested in Marcel Duchamp's work at an early stage of my art history studies. His then most important piece, The Bride Stripped Bare by her Bachelors, Even, particularly fascinated me and I wished to understand the complexity of the work itself. I also wanted to learn more about the personality and psyche of this artist.For several years I lived in Philadelphia, and spent many Sunday afternoons in the Philadelphia Museum of Art studying, evaluating and appreciating Duchamp's works which can be found in the Arensberg Collection. I obtained Richard Hamilton's translation of the Green Box1 and used it as Duchamp wished--reading it along with a visual study of The Bride Stripped Bare.During my residence in Philadelphia and, shortly after his death, Duchamp's final work was unveiled. Upon further study of his total work and the writings about him, I experienced in several dimensions the message of his art and felt that this new writing, this thesis, needed to be done. I could not accept the frustration, castration, negation, and non-aesthetic that was read into his work by many critics. Duchamp was a revolutionary in art, yes--but there was an erotic joy, a sensuous aesthetic sensitivity to his form, be it created or found, and a continuous desire on his part to extend man's aesthetic awareness to new areas of life experience.This thesis presents a critical re-evaluation of Marcel Duchamp's two works: first, The Bride Stripped Bare by her Bachelors, Even; and secondly, Etant Donnés: 1° la chute d'eau, 2° le gaz d'éclairage, which is the concern of chapter two.Because of the nature of these two works of art, it was necessary to discuss and analyse iconographically, in chapter one, various other works -- following their development and recurrences as symbolic images. Several statements by writers and critics are also re-evaluated, mainly those referring to an erotic pessimism reflected in Duchamp's work.An important guide line for this study has been the Green Box. It, along with other writings and staements, revels Duchamp as a sensitive, highly intellectual artist ready for constant changes. From the material within the Green Box is woven the thread for the final content -- the positive, erotic message and the aesthetic experience.1 Duchamp saved all of the notes, sketches, and drawings related to The Bride Stripped Bare in a green box, which he later published, titled the Green Box. A typographic version of the notes, translated by George Heard Hamilton, was prepared by Richard Hamilton, titled The Bride Stripped Bare by her Bachelors, Even (London: Percy Lund, Humphries and Co. Ltd., 1960).