The question of what defines film noir, and what sort of category it is, provoke continuing debate.[5] "We'd be oversimplifying things in calling film noir oneiric, strange, erotic, ambivalent, and cruel ..."—this set of attributes constitutes the first of many attempts to define film noir made by French critics Raymond Borde [fr] and Étienne Chaumeton in their 1955 book Panorama du film noir américain 1941–1953 (A Panorama of American Film Noir), the original and seminal extended treatment of the subject.[6] They emphasize that not every noir film embodies all five attributes in equal measure—one might be more dreamlike; another, particularly brutal.[7] The authors' caveats and repeated efforts at alternative definition have been echoed in subsequent scholarship, but in the words of cinema historian Mark Bould, film noir remains an "elusive phenomenon