 Finally, a question might be raised about the relation of Du Bois’s double-consciousness conception and the sorts of self-doubts, troubled feelings, and “identity issues” that have been linked to biracial or mixed-race appearance or identity in our persisting, harshly racialized American social world. The racist ideologies accompanying and justifying white supremacy, and the mores and systems of “etiquette” governing “race relations” in racially hierarchical social conditions, have presented particular difficulties for persons of ambiguous racial descent, visibly marked as brought into being by “race mixing”. Often mixed-race persons have encountered hostility and suspicion from “both sides”, from each of the distinct races of which they are mixed. Sometimes they are deemed weak or inferior just because they are mixed, as Naomi Zack documents in her Race and Mixed-Race (1993: chapters 11, 12). Indeed, Du Bois was himself personally deeply familiar with this issue, as he relates, for instance, from his university days in Berlin. His “most interesting” professor there was Heinrich von Trietschke;