WARNING: THIS ENTRY, LIKE MOST OF MY ANALYSES, IS A RELENTLESS STREAM OF SPOILERS.
There Will Be Blood begs a question -- was Daniel Plainview always an asshole, even when he came from a humble station and chipped away at rocks for silver? Was his early appearance of earnestness simply cover for a calculating, malicious nihilist? Or is this the story of his fall from earthy humility into the madness of alienated wealth? Is it the oil and the money that are evil? Or is it simply human nature, poisoned at the root, fertile ground for corruption and betrayal?
Your interpretation of Daniel's actions must answer that question, and it will, in turn, retroactively color your experience of the whole film. Read as a fallen hero, a failed father figure, Daniel Plainview is a study in disillusionment, a showcase for the destructive power of wealth and obsession. This story is a story of a fall from grace, the story of Adam or Anakin Skywalker. However, read strictly as a villain, Daniel Plainview becomes a culmination of all of humanity's most horrible potentialities. He becomes the type of evil, cruel, unredeemable character rarely found in the bible, or in any literature... a Grendel before he was humanized by Gardner, a Cormac McCarthy antagonist. According to this interpretation, his final sadistic moments are the blossoming of a man who was always rotten deep down.
When a question like this is just floating in the air over a narrative arc, it's easy to take the middle path: "Well, I think he always had the innate potential to be evil, but it was the oil and the money that hardened him into a villain." It's the most logical answer, but also a little bit of a cop-out as to "human nature," as it were. But it's not an open-ended question... in There Will Be Blood, it's a strict binary, and it hinges on a particular point, right at the end of the movie.
That point: when Daniel tells his son that he never cared about him, is he lying, just to injure his son in a moment of passion? Or is he telling the truth?
If Daniel is lying about these things, it means that his concern for his son -- his earnestness as a father -- was real, at least at the beginning. These damning claims are merely weapons that Daniel Plainview is using, here at the end of his life, to scorch the barren earth of his own relationships and good name. But if Daniel is telling the truth to HW, it means that his whole life, his every act of kindness and humanity has been inauthentic, part of his pursuit of profit. It's a striking paradox: if Daniel is lying at the end of his life, it's to hide the fact that he was once a decent human being. If he is telling the truth, it's only to reveal that his whole life has been a lie.
In this final monologue to HW, Daniel offers no less than a sudden, complete revisionist history of his own whole life. This development splits his life into two competing narratives, as revisionist histories tend to do with their subjects. Though you might prioritize one narrative over the other, you can never efface either of them from your image of Daniel... he now exists in two parallel universes: one where he was a practical, competitive man who at the very least loved his son; another where his whole life was a con, an offense against our most basic human sensibilities. In the former universe, wealth and oil have the power to rob man of his humanity. In the second universe, man never had any humanity, except what he fabricated to manipulate himself and the people around him.
But if the truth of Daniel's poisonous confession is the pivot point in this Janus-faced narrative, then we have to consider the damage wrought by these events upon truth itself. There Will Be Blood doesn't just let truth stand, unmolested, to be assessed and accounted for. Rather, the film shows how power and wealth, infiltrating the society and the soul, begin to break down the integrity of truth. Eli Sunday is that part of the story.
Eli Sunday may stand in for "faith" and "religion," but on a deeper level, he represents the universal ideal of "truth." He lays claim to the power of prophecy and revelation; he sees right past Daniel Plainview's neighborly facade when they sit down together at the dinner table. He repeatedly faces down authority, rendering his own father meek and disenfranchised -- a case study in speaking truth to power. And when Daniel Plainview needs to buy Bandy's farm, and supplicates himself before the church, Eli uses "the truth"... or at least a certain variation on it... to put his own final seal of authority upon the oil man.
At this pivotal point, Daniel Plainview is forced to betray himself by conceding his own narrative. In his own version of his life, he did not "abandon" his son so much as simply send him away out of fatherly concern, and when Eli forces him to confront this darker side of the truth, he is exploiting Daniel's fatal existential weakness. In the process, however, Eli effectively destroys himself, because he also betrays the sanctity of truth itself. Using "truth" and confession in this cynical way, Eli turns it into a tool of power, a mere corollary to a world governed by dominance and ambition.
Daniel is the lord of this world, and as soon as he gets the chance, he turns truth -- now enslaved by the whims of power -- back upon Eli as a weapon. Just as Eli poisoned Daniel's personal narrative, so Daniel forces Eli to uproot his own, using the leverage of wealth and influence to force a confession out of the prophet. "I am a false prophet! God is a superstition!" is not entirely the truth, but it isn't a lie, either, especially coming from the lips of the prophet Eli. It's an effacement, a disfigurement of truth, a twisting of the truth in Daniel's hand. And this betrayal of the truth, this malignant counter-revelation, this toxic confession, is as much a part of Eli's death as a bowling pin to the head.
I suspect that Daniel's rotten self-image... his insidious narrative of his own motives... really started taking shape when he discovered that his "brother" was a stranger, clinging to a false identity to ride sidecar on Daniel's success. Daniel's interaction with Henry seemed to be his last chance at trust, the final departure point where Daniel might have placed his faith in a comrade. When Daniel discovers that Henry is a fraud, he finally finds that familial love and cynical exploitation are irresolvably tangled in his mind. At this moment, he begins to doubt all human connection, including his own affection for his son. If his last chance of brotherhood was a mere facade, corrupted by money and lies, how can he trust his own claim to fatherhood any more?
There are endless echoes of the bible in There Will Be Blood, but there are also echoes of Heisenberg and Foucault. Perhaps Daniel Plainview's soul isn't determined at the time it's expressed... maybe it isn't determined until many years later, when he interprets it in the most negative light, crafting a vicious and inhuman narrative with which to bludgeon his son. Maybe, if he had just been more charitable to himself, Daniel Plainview would have retroactively determined his life as the tragic downward spiral of a decent businessman. Or maybe, conversely, the interpretation is meaningless -- maybe "truth" isn't even a thing in this world of wealth and oil and exploitation of the land and community. Maybe, as Foucault has implied, the truth is just a shroud draped over an infernal machine, a grinding apparatus of power and cynicism and influence.
This isn't the first or last word, by a long shot -- it's a wide-open film, full of recessed spaces for interpretation. Eli's relationship with Paul is one of its great unexplored mysteries, as is Eli's claim to moral righteousness. But at the very least, we've made a reasonable start at teasing out some of those complexities and ambiguities, and finding some meaning in a tragic, terrifying film with a nihilist soul.