Besides science fiction， humor is another essential feature of Vonnegut's narrative that has caused much controversy。 Scholars generally agree that Vonnegut is a superb humorist， but they disagree as to whether there are serious messages behind the mocking voice。Earlier critics were especially doubtful about this。Whereas C。D。B。Bryan was among the earliest critics to call attention to Vonnegut， assessing him as“the most readable and amusing of the new humorist”，he complained that Vonnegut“takes very little seriously”，and believed this prevented the author from being a major satirist on the order of John Barth（31）。Likewise， Robert Scholes called the black humorists—Vonnegut among them—“fabulators”instead of satirists， because they lacked“the rhetoric of moral certainty”that readers expected from satire（“Kurt Vonnegut and Black Humor”74）。In his later New York Times Book Review of Slaughterhouse-Five， though， Scholes became more affrmative。He succinctly summarized the moral taught in Slaughterhouse-Five as“Be kind。Don't hurt”and lauded the healing effect of Vonnegut's humor， ranking him among the“stoic Comedians”（“[History as Fabulation]：Slaughterhouse-Five”37）。
Opinions of Charles Thomas Samuels and Peter S。 Prescott were completely harsh。Samuels refused to acknowledge any worth in Vonnegut's writing， except“what his rise itself indicates：ours is an age in which adolescent ridicule can become a mode of upward mobility”。He found Vonnegut's characters“one-dimensional grotesques impersonating people”（qtd。in Reed 1972：21）。Prescott showed his outrage even more fiercely commenting on Breakfast of Champions。“Manure， of course。Pretentious， hypocritical manure，”he declared，“From time to time， it's nice to have a book you can hate[……]and I hate this book for its preciousness， its condescension to its characters， its self-indulgence and its facile fatalism”（39）。
Is Vonnegut trying to tell us something in his novels？Peter Reed's answer was both“Yes”and“No”。 He concluded his 1972 examination of Vonnegut's six early novels by saying that“[t]o see his novels as explaining or answering large philosophical questions would be to do them a disservice。Or， to put it another way， his explanation might be that there is much that we do not， and perhaps cannot know， and that to embrace formulae which seem to offer answers is dangerous”。For him， Vonnegut's special strength lay in his warning against the desire for ultimate answers to universal questions。The lesson Vonnegut taught us was that“the world[……]appears absurd， and life within it generally seems ultimately meaningless”（1972：205，206）。
This leads to another baffing question：Is Vonnegut a nihilist？Is he a pessimist？Or， to put it another way， is he， like his most famous protagonist Billy Pilgrim， a moral quietist who adopts fatalist Tralfamadorianism and determines on the withdrawal from any active social participation？Many critics of the 1970s answered the questions affirmatively。 They treated Vonnegut as an absurdist who viewed the world as ridiculous and meaningless and who thus assumed a worldview of“total resignation”（Harris 75），hiding his despair behind“escapist， regressive fantasies”（Edelstern 129）and dark laughter。Ihab Hassan（1973）named Vonnegut a fatalist。John Gardner suggested that it was natural to see Vonnegut as a nihilist， for Vonnegut's writing suffered from a“lack of commitment”（qtd。in Merrill 1990：13）。Josephine Hendin believed that“spacing out is Vonnegut's answer to death， war， and human glaciers”and“that dumbness is precisely Vonnegut's solution”in Slaughterhouse-Five（qtd。in Merrill 1990：13）。David Bosworth contended in“The Literature of Awe”that what Vonnegut recommended was“pessimism， cynicism， resignation， despair”（23）。Shallow or biased as these readings might be， they were revealing facts that during the 1970s pessimism and resignation to determinism were widely acknowledged as the trademarks of Vonnegut's fction。
Other critics tried to counterbalance this pessimistic and fatalistic reading。 Doris Lessing argued that“what Vonnegut deals with， always， is responsibility”and that Vonnegut refused to succumb to“the new and general feeling of helplessness”（46）Gros-Louis recommended readers to distinguish Vonnegut from Billy Pilgrim， for Vonnegut represented pacifsm and Billy a form of Tralfamadorian passivity。Peter Reed， Klinkowitz， and Robert Merrill all made conscientious efforts to establish a more hopeful image of the author， but somehow， they found it hard to reconcile the“humane optimism”they tried to foreground and the dark pessimism that so powerfully prevailed in most of his novels。
There was a general diminish in the body of criticism on Vonnegut in the 1980s and unfavorable criticism continued， accusing him of“adolescent stoicism”（Aldridge 7），“sentimental whimsy”（Karl 174），and“bewilderment and resignation”（Saltzman 90）。 Nonetheless， some studies showed a better understanding of Vonnegut's art and messages。 Kathryn Hume published three articles in 1982，trying to unravel the tension between“the pessimism born of experience and the optimism stemming from background and value”（201）。Instead of viewing him as nihilistic， Hume believed Vonnegut had struggled to work out a value system for the contemporary age。“He is no Pollyanna， but neither is he totally pessimistic or cynical，”she contended，“His last three novels[namely， Breakfast of Champions， Slapstick， and Jailbird]take affirmative stances and work to support these in the face of humanity's inhumanity”（214）。
Hume's position marked an important turn in Vonnegut criticism。 An optimistic Vonnegut became distinct by the 1990s。Leonard Mustazza's approach from the myth of Eden，Lawrence Broer's psychoanalytical investigation of madness（1994），Kevin Boon's study in view of the theory of chaos（1997），Todd Davis'examination from the perspective of postmodernism and ethics（2006），and Gilbert McInnis’attempt at uncovering an evolutionary mythology in Vonnegut’s writings（2011）all endeavored to present a Vonnegut who was dedicated to maintaining the dignity and beauty of humanity in face of violence， disaster， and chaos。
If earlier critics tended to evaluate Vonnegut's philosophy in the dichotomous formula of“either……or”，emphasizing one aspect over the other（usually pessimism over optimism），critics of the recent years were more inclined to accept the coexistence of both。 Lawrence Broer， for example， saw the conficting elements of fatalism and optimism as the manifestation of the character's schizophrenic split of the self， a split into“a self that affrms and a self that denies”。For him， the attempts at resolving the combat of these warring identities constituted the“psychoanalytic plot”central to Vonnegut's novels。Although it was justifable for critics to read Vonnegut as a cosmic pessimist， Broer contended， it was wrong to ignore the“spiritual twin”of the nihilistic voice in the protagonists，“the efforts of a healthy， yearning， creative self to brave the life struggle， to develop the awareness and courage to act against self-imprisoning cat's cradles and to determine its own identity in a world of mechanistic conformity and anonymity”（10）。While the fatalistic characters were what Vonnegut warned us against， the positive yearning was what he advocated。For Broer， Vonnegut's“creative craziness”served for both himself and the reader as a therapy to regain equilibrium in a mad and aggressive world。
Boon used the chaos theory to approach the paradoxical coexistence of pessimism and optimism。 He argued that although Vonnegut departed from the modernist writers in that instead of“bringing order to chaos”，he would“bring chaos to order”（KV's words in Breakfast of Champions 210），his universe of disorder and indeterminacy was not without hope。“Vonnegut clearly advocates a world that would use more human kindness，”observed Boon（1997：31）。Human kindness to Vonnegut was essential to help people fend off despair。Therefore，“Vonnegut's universe is one where both determinacy and indeterminacy serve a function：determinacy provides human beings with some sense of stability and indeterminacy provides human beings with a universe rich with variety and possibility”（1997：33）。In other words， Vonnegut bridged the modernist closure and the postmodernist nihilism， adopting postmodernist techniques， while hanging on to the modernist ideals of meaning and value。