There are many different ways for one to interpret The Trial, a book by the Czech-born German-speaking Jew Franz Kafka. Some are overlapping while some are contradictory, yet this should hardly be a worry; contradictions lie at the heart of the work of every great writer while being absent from the confident, simple-minded work of the second-rate. The fact contradictions exist is what spurs the great to write in the first place.
Spoilers, of course, follow; conversely, what follows will probably make sense even if you have not read the book. We are dealing here with very general matters of interest to us all.
Kafka wrote The Trial after he ended an engagement with a woman who lived in a distant city and whose friends and family had a great influence over the course of their relationship. He writes in his diaries that he felt as if he was awaiting judgement from an alien court as to whether the marriage would proceed, and he also seems to have fallen for one of the girls who was an intermediary between him and his fiancé. Both of these facts find an echo in The Trial, where the whole future of the the protagonist, one Josef K., rests on the judgements of an arcane legal system of which he has no comprehension. K. - as he is known throughout the work - also takes a fancy to almost every girl he encounters, and especially the one that stands as the intermediary between him and his trial advocate, who is his best hope of influencing the proceedings against him.
The most fruitful way of which I am aware to read The Trial is to view it as a parable of one man's search to justify his own existence to himself. K. wakes up one morning to find his usual routine has been interrupted by the arrival of two men who tell him that he is under arrest for an unspecified crime and that the trial has begun; the close reader will observe that they do not enter the room until he requests them to, and that they do not physically compel him in any way. It is K. himself who allows this process to begin, although he is deceived at the outset about the nature of this process.
K. soon discovers that he is not to be actually incarcerated and is still a free man; what takes him much longer to discover is that he has been left with his freedom so that he has the rope with which to hang himself. It soon becomes clear that K. is not to be incarcerated because it is his life itself that the court by which he is charged is interested in, and that this court counts everyone in the world as a witness, and not a small number of people as its direct agents; it is this aspect of the novel that makes it appear to anticipate totalitarianism so well.
But Kafka's point does not seem to be political nor a prophetic foreboding of Nazi Germany. What Kafka is evoking is man's capacity for rootless metaphysical speculation about the nature of his own existence, and his ability to doubt and question this existence; that is why K. is on trial for his life but the charge is not precisely defined. It is the inherent Why? of his life that is on trial. Kafka is no stranger to this theme and addresses it in an aphorism elsewhere, where he states: "He found the Archimedean point, but he used it against himself; it seems that he was permitted to find it only under these conditions". Kafka's point about modern man is that he learnt to transform his whole world by questioning everything and embracing science, but that ultimately he also had to question himself. And this questioning of himself could kill him because he could never reach a satisfactory answer to his own Why?.
K. is on trial for his very existence but almost every time that he steps out of his everyday life to participate in the business of the trial, he does so of his own volition. He started this questioning of the Why? himself but now he has begun he cannot resist pursuing it. He is told by those familiar with the legal system that official hearings can easily be skipped and that trials can be merrily elongated for years with minimal effort and never reaching a verdict; but K. is not to be placated and is desperate to quickly and actively prove his innocence of the unspecified crime. His entire life story becomes the subject matter of depositions prepared for the court as he is forced to go over every decision he has ever made, and he finds it impossible to get the whole business out of his mind to the extent that it begins to interfere with his job at the bank, which K. clearly finds less compelling than the trial.
Initially K. clings to the notion that the skills that have served him so well in his very bourgeois job - above all his reason - will allow him to quickly see off the trial and prove his innocence. But as the arcane rules of the court and its incomprehensible nature becomes clear he realizes that human reason is inadequate to the task; just as our reason cannot divine the answer to our Why?, because the answer lays beyond the realm of things that can be reasonably proven. These matters must be the subject of felt insight or faith, things that K. becomes aware of because he does not have them; and when he hence realizes the weakness of mere reason, he begins to even have doubts about his work at the bank. Doubt has begun to infect every aspect of his life.
As K. continues with his attempts to prove his innocence, he encounters various people who claim they can help him. They all offer a different route to success, claiming special influence over the court; but all stress that there is a deep futility in his quest to prove his innocence, and that once the trial has begun virtually no-one achieves this happy ending. K. has begun down a track that he cannot retreat from, and so the best he can hope for is merely to postpone the result.
He meets an artist who tells him that he has heard myths of people who were found innocent in the highest court of them all, people who managed to beat the system; he does not know the details of their cases, but he has painted some. Kafka's illustration of the redemptive but ultimately futile power of art is delightful: the artist tells K. that he can provide some relief, a temporary removal of life's warts which will take the pain of the trial from over his head for some time, but which cannot last for ever. Eventually reality will return and the trial will be reactivated, and the artist can only provide complete relief for those who are entirely innocent. So this means the artist can only help those whose life is in fact already a work of art, complete and perfect and meaningful in itself; and such people exist only in myth.
Finally K. meets a priest, who tells him that he is the "prison warder". A priest as a prison warder is natural enough if we are predisposed to see religion as a force which turns life into a prison, where we are constantly watched and judged and not free. But that is not the point here. The priest is the one who has the most illuminating things to say about the path to understanding the law, or the Why?. He tells K. a long parable about a man who seeks access to the law and yet is unable to access it, and covers many different intepretations of why he cannot get to it; the ultimately futility of the quest is illustrated by the fact K. is not heartened by any of these explanations, but concludes that "the lie is fundamental to world order". Or, as Nietzsche wrote, the conditions of life might include error; falsehood might be needed to sustain life, whereas the futile quest for the inaccessible truth of the Why? leads only to destruction.
And it is to this destruction that K. now hastens, as he co-operates with functionaries of the court who take him from his room, out of the city, and kill him. He has killed himself through his quest by destroying any reason he had to live. The very fact of embarking on the quest for a reason predisposed him to failure, because the quest can only fail. The capacities that we like to think make us fundamentally human - our reason, our faith, our empathy - failed him at the last. As so as he dies, his final verdict on his passing is this: "Like a dog!"