The Robert Langdon book series is named after Robert Langdon, the protagonist of the novels by American author Dan Brown. Langdon is portrayed as a Harvard University professor of religious iconology and symbology, a fictional field related to the study of historic symbols, which is not methodologically connected to the actual discipline of semiotics. Brown's novels that feature the lead character also include historical themes and Christianity as motifs, and as a result have generated controversy. Brown states on his website that his books are not anti-Christian, and that he is on a "constant spiritual journey" himself.