Evasion – "When a prisoner of style escapes, it's called an evasion" (Tom Sawyer, in Adventures of Huckleberry Finn, p. 333).
Existentialism – The dictionary in my office defines it this way: "a literary and philosophic cult of nihilism and pessimism, popularized in France after World War II . . . it holds that each man exists as an individual in a purposeless universe, and that he must oppose his hostile environment through the exercise of his free will." I agree that the word "existentialism" came into being with French writers like Sartre, but the idea it articulates is already being explored and expressed by American (and other) writers long before World War II. To me, "existentialism" is the appropriate word to describe what Jake means, in Hemingway's 1926 novel, when he thinks that "All I wanted to know was how to live in it. Maybe if you found out how to live in it you learned from that what it was all about" (p. 152). I think it's also a good label for Wallace Stevens' program of "the imagination pressing back against the pressure of reality," creating through acts of art and will "a supreme fiction" that can supply "the idea of order" in a universe defined as "the nothing that is" there. You can even think of Henry Fleming setting out to be an existentialist hero at the beginning of Crane's Red Badge, when he decides that to find out who he is and what life is when he goes into battle, he'll have to "experiment" in an unknown world, "accumulate information of himself" (p. 10) -- though to me he keeps retreating from the challenge of that mode of existence to seek shelter in such conventional or traditional fictions as a "soft and eternal peace," rather than the ongoing need to enact a meaningful life that we see in Jake, Stevens and those bull fighters in the terrain of the bull.