In Vizenor's subsequent novels, he used a shifting and overlapping cast of trickster figures in settings ranging from China to White Earth Reservation to the University of Kent. Frequently quoting European philosophers such as Umberto Eco, Roland Barthes and Jean Baudrillard, Vizenor has written a fiction that is allusive, humorous and playful, but deeply serious in portraying the state of Native America. He has refused to romanticize the figure of the Native and opposes continued oppression. Vizenor's major theme is that the idea of "Indian" as one people was an "invention" of European invaders. Before Columbus arrived, no one defined Indian as other; there were only the indigenous peoples of various tribes (such as Anishinaabe or Dakota). (They defined "other" among themselves, often divided by languages and associated cultures.)