The traditional interpretation of "Cubism", formulated post facto as a means of understanding the works of Braque and Picasso, has affected our appreciation of other twentieth-century artists. It is difficult to apply to painters such as Jean Metzinger, Albert Gleizes, Robert Delaunay and Henri Le Fauconnier, whose fundamental differences from traditional Cubism compelled Kahnweiler to question their right to be called Cubists at all. According to Daniel Robbins, "To suggest that merely because these artists developed differently or varied from the traditional pattern they deserved to be relegated to a secondary or satellite role in Cubism is a profound mistake."