Reynolds introduces the book's anti-textbook premise and traces racist ideas to their precise origin: Gomes Eanes de Zurara's 1453 chronicle justifying Prince Henry the Navigator's slave raids on the African coast.

The book traces racist ideas from Portugal to the American colonies through the figure of Cotton Mather, the Puritan minister who synthesized religious justification with emerging pseudo-scientific claims, producing a new, more durable form of racist ideology.

Reynolds examines Thomas Jefferson as the American founding's central paradox: the man who wrote 'all men are created equal' while owning enslaved people and writing pseudo-scientific arguments for Black inferiority, showing how assimilationist thinking can coexist with professed ideals of equality.

Reynolds examines abolitionism through the figure of William Lloyd Garrison, showing how the mainstream antislavery movement carried assimilationist assumptions, and introduces the concept of 'uplift suasion' — the belief that Black people could defeat racism by proving their humanity.

Reynolds traces Du Bois's intellectual journey from his early assimilationist theory of the 'Talented Tenth' through his later, more radical antiracist analysis, showing how even the most brilliant Black intellectual of his era had to fight against the assimilationist assumptions embedded in his own education.

Reynolds brings the history to the present through Angela Davis, showing what an uncompromisingly antiracist position looks like in practice — and at what cost — before turning to the contemporary landscape of mass incarceration, the war on drugs, and the evolution of racist ideas into colorblind and post-racial language.

Reynolds brings the argument into the reader's present, cataloguing the forms racist ideas take in contemporary American life — social media, school curricula, 'respectability politics,' post-racialism — before making the book's final, direct demand: choose your camp and act from it.

Reynolds reflects on the process of translating Kendi's Stamped from the Beginning for a younger audience, making explicit the book's argument about the accessibility of ideas and who gets to be a reader of intellectual history.