The fight against racism developed momentum in the aftermath of the Second World War, but for much of that period it relied on a narrow, static, and largely ahistorical account of racism as a set of ideas rooted in biological science. Although this portrayal of racism had clear shortcomings that were exposed at the time by Marxist theorists like Oliver Cromwell Cox, it did serve the useful function of establishing a consensus against its target. A clear and suitably narrow definition of racism may be appropriate in legal contexts where there is also a need to establish the intentions of the individuals so accused by scrutinizing their language. Nevertheless, numerous theorists have now shown the shortcomings of this approach when it comes to identifying the determining role of the societal practices in which these individual acts of racism occur. For example, it has been shown to be ill-equipped to address what Stokely Carmichael and Charles V. Hamilton called “institutional racism.” Or, to offer another example, the attack on racism has focused on challenging the scientific concept of biological races but this left intact so-called cultural racism, even to the point whereby South African supporters of apartheid did not feel challenged by UNESCO’s 1950 Statement on Race, which had adopted that strategy. Although in philosophical circles there are still adherents of some narrow definitions of racism in terms of either ideas or sensibilities, the dominant tendency today, especially among historians and sociologists, is to multiply the historical periods and forms in which racism can be found. On this basis it would seem that racism is broad, fluid, and should be approached historically. One might even think of racism as plural: racisms. But if we examine the history of racism more closely we have reason to believe that sometimes the racism of one period (for example, that deployed to justify slavery), while superficially very different from the racism that succeeded it (for example, the biopolitical racism identified by Foucault and others), was in part shaped by earlier forms. This dynamic character of racism needs to be reflected in our theories and in a first step I promote a modified version of the dialectical approaches to racism found in C. L. R. James, Frantz Fanon, and especially Jean-Paul Sartre. I also argue that a dialectical approach offers fresh resources for exploring the relations of anti-Semitism and so-called Islamophobia or anti-Muslim sentiment to racism, especially anti-Black racism.