Knowing truth--discovering truth--is a much more complicated concept/process than it appears to be at first glance. Different authors have different views on exactly how one should go about "knowing truth." These views influence what the authors write and publish, and from their works we can discern their individual views on the discovery and comprehension of truth.
Realism: Henry James
Henry James is widely considered to be a Realist writer. This designation stems from the objective view of truth that he exhibits in his writing. Towards the end of his work "The Beast in the Jungle," James writes:
"The escape would have been to love her; then, then he would have lived. She had lived--who could say now with what passion?--since she had loved him for himself; whereas he had never thought of her (ah, how hugely it glared at him!) but in the chill of his egotism and the light of her use."
Throughout the entire story, James' protagonist, John Marcher, is living his life with an overwhelming feeling of destiny: that something significant is to happen in his life. Only after his female confidant and close friend had died did he realize that his destiny had been "to love her. Marcher had not perceived that romance could be the true culmination of his sense of destiny, but in spite of his misguided perceptions James leads us to believe that she truly was his destiny. It was an objective truth, even though he did not know what the truth was.
Modernism: T.S. Eliot
While James thought truth was absolutely objective, T.S. Eliot took an entirely different spin on the topic. From Eliot's modernist perspective, reality can be derived from works of art. At the conclusion of "The Wasteland" after he had been referencing numerous works of art, Eliot penned: "These fragments I have shored against my ruins. Why then Ile fit you." The fragments to which Eliot refers are the works of art he had been referencing. In this line of poetry he is essentially saying that he is pulling all of the shards of art together against his foundation in order to fortify himself--in order to know or discover truth. Essentially, though, Eliot is not discovering truth, but rather using imagination to create it. Think about it for a minute: most of the works of art he is "shoring against [his] ruins" were created out of someone's imagination. They are fictional. In addition to the fictional nature of these works, Eliot is also individually selecting which works to use as supports, thereby creating a second layer of creative imagination.
Post-Modernism: Thomas Pynchon
Hot on the heels of Modernism came the Postmodernist movement. Postmodernist writers generally emphasize the subjectivity of experiences, and the concept that individuals create their own truth or reality. From his writing we can see that Thomas Pynchon subscribed to that school of thought. Throughout his story "Entropy," Pynchon presents the perspectives of two different groups of people: the man and the woman in the upstairs apartment and the party in the lower apartment. I suggest that Pynchon is showing us two different "realities." In the upper apartment the man and the woman are living in the reality of entropy. They think about the laws of thermodynamics, they observe a constant temperature outside their apartment for several days in a row, and then the woman ultimately ends their lives in their truth of entropy by smashing the window. In contrast, the people at the party below are living the truth of jazz, booze, and relationships. They know nothing of the truth of entropy in the apartment above, so it is not "true" for them. Pynchon is telling us that truth is totally subjective and based solely on individual perceptions.
As we can see from the differences illustrated above, many people and authors hold to differing views of how truth is known or discovered. James and the Realists claim that truth is objective and does not change, even if we do not know what the truth actually is. Eliot and the Modernists say that are and imagination create truth. Finally, the Postmodernists claim that truth is entirely subjective and inherently dependent on each individual's perceptions.
So who is right? Each group presents mutually exclusive claims, so they can't all be right. Since truth cannot be both objective and subjective, Postmodernism's view cannot stand since they claim that the Realist's perspective of objectivity is also valid, which invalidates their view. Modernism boils down to essentially a Postmodernism based on art and imagination, so out of these three perspectives, Realism is the most probable. In the end, it seems like all of this "progression" in literary theory amounts to little more than mind benders and good stories to read, and not any real advancement in the understanding of how we know truth.
Or does it?
+ The Beast in the Jungle by Henry James.
+ The Wasteland by T.S. Eliot.
+ "Entropy" by Thomas Pynchon.