What ideas he has, what unnaturalness, what paroxysms of nonsense, what bestiality of thought erupts as soon as he is prevented just a little from being a beast in deed. ... Too long, the earth has been a madhouse! ... the Greek gods, those reflections of noble and autocratic men, in whom the animal in man felt deified and did not lacerate itself, did not rage against itself! For the longest time these Greeks used their gods precisely so as to ward off the "bad conscience," so as to be able to rejoice in their freedom of soul—the very opposite of the use to which Christianity put its God. ... We modern men are the heirs of the conscience-vivisection and self-torture of millennia. - (Nietzsche, Genealogy of Morals, Section 23 of the Second Essay)
The drama at the sanatorium in Thomas Mann's The Magic Mountain, the air of opaqueness and madness in Kafka's The Trial, the neuroticism of the narration and narrator in the major novels of Proust, Beckett, and Joyce. All of these books that are hailed as great works of modernist literature share a lot in common with Nietszche's diagnosis of the modern condition. The animal lives below the surface in these novels, bubbling up to the top and sometimes even bursting forth. To me, what makes these novels great works of modernism is the way in which the bestiality of thought is put on display, while at the same time honoring the animal.