The contributions of Gaston Bachelard to the history and philosophy of science are not very well known in the United States. This thesis traces the particular characteristics of Bachelard's epistemology within the context of early twentieth century French culture and science. Bachelard began his career in philosophy comparatively late in life and although his background in mathematics and physics was reflected in his philosophical approach to science, he belonged more to the French intellectual avant-garde than to the traditional philosophies of positivism and pragmatism defended by the Third Republic. Bachelard's writings represent an important contribution to a new vocabulary in epistemology, and they influenced scholars such as Georges Canguilhen, Alexandre Koyré, Louis Althusser and Michel Foucault. His works definitely deserve wider exposure, as they easily connect with problems that American scholars pursue today in Science Studies. / Master of Science