Few issues in the United States today are as controversial as diversity, equity and inclusion -- commonly referred to as DEI. Although the term didn't come into common usage until the 21st century, DEI is best understood as the latest stage in a long American project. Its egalitarian principles are seen in America's founding documents , and its roots lie in landmark 20th-century efforts such as the 1964 Civil Rights Act and affirmative action policies , as well as movements for racial justice,