Why Literary Periods Mattered explains how historical contrast became central to literary study, and why it remained institutionally central in spite of critical controversy about literature itself. Organizing literary history around contrast rather than causal continuity helped literature departments separate themselves from departments of history. But critics' long reliance on a rhetoric of contrasted movements and fateful turns has produced important blind spots in the discipline. In the twenty-first century, Underwood argues, literary study may need digital technology in particular to develop new methods of reasoning about gradual, continuous change.