Difficulties are encountered in any discussion of Copland's style, for his works cover the spectrum from harsh, dissonant works to folk music. To avoid the task of defining a style which encompasses this array of vastly different pieces, a sharp distinction is frequently made between the abstract and popular works. However, Copland has repeatedly objected to such categorization, claiming that he composed from a single vision. A careful examination of his total output proves the validity of his claim. Many common characteristics are found throughout works from all categories and time periods. These traits include a basic economy of materials, emphasis on thirds, consistent method of development, use of declamation, jazz-influenced rhythms, cyclicism, and a slow/fast/slow sequence of movements, as well as within single movements. This document uses the Piano Sonata as a model of Copland's style, for it exemplifies these characteristics more clearly than any other major piece for piano. By making numerous comparisons with other works, Copland's single vision is revealed.