This volume gathers new essays on A. R. Ammons's long poems by many of the most influential critics of contemporary American poetry, including Helen Vendler, Marjorie Perloff, and Willard Spiegelman. It will serve for years to come as an important critical text on a vast body of work by one of the most prolific and innovative practitioners of the long poem in post-World War II American poetry. Complexities of Motion, then, is a collection of new critical articles on the entire range of Ammons's longer poems, beginning with Tape for the Turn of the Year (1965) and culminating with Glare (1997).