The sacred king was the cornerstone of Frazer's theories about ancient civilizations. In his work, he postulated that in the past, the life and eventual death of kings represented and growth and death of the vegetation, a "dying and reviving god". This human king provided for his people for a time and then eventually was sacrificed back to the earth. (I have some problems with this theory... namely that back in ye oldeny times most people were nomadic and didn't do a ton of agriculture... but this is about lit theory and therefore my historical issues with it really aren't relevant.) In any case, this connects to the fact that both in ancient and far more modern history, some kings are viewed as sacred beings. This could mean that the king was credited with good fortune. Or it could mean that your people view you as responsible for their well-being and sacrifice you in order to get a better harvest next year.
The maimed king (also known as the Fisher King, as he was referred to in T.S. Eliot's poem The Waste Land) seems to come from Arthurian legend. In the tales, this king was wounded so that he suffered from impotence, and his lack of fertility affected the earth around him and turned it into a barren wasteland. This legend is super freaking weird in all of its incarnations (there's a version where this king asks his followers to cut off his head and then his head keeps talking and keeps them all company on their trip back to Britain idk idk guys the Celts were weird). In any case, when purehearted people eventually come fetch the Grail he was hanging onto and this somehow heals him, his restoration represents the growth of vegetation in spring. Rebirth, if you like.
SO. These are cool and all, but not terribly interesting concepts unless you're super into agriculture and ye olde civilizations that may or may not have been nomadic. So why talk about them at all?
Because I think that these are necessary concepts if you want to understand what sacrificial kingship is and why it works. The idea of a king being responsible for the fate of his people, and being willing to lay down his life for their good, is deeply embedded in not just one culture, but essentially every culture. While history tells us that kings are flawed and often corrupt, our legends and mythology tell us a very different tale. Belief in the goodness and rightness of our kings is practically part of our DNA.
It's why characters like Aragorn work in fiction. We see from his introduction in The Fellowship of the Ring that although Aragorn is a good leader and has royal blood, he has no desire to be king and happily plays around in the mud while the stewards of Gondor do their thing. (Yes, I know that the films gave him all this inner conflict about being Isildur's heir, because of course if your great-great-great-great-great-whatever was susceptible to corruption, so are you, because that is totally how ancestry works. This isn't in the books and it was stupid anyway so I don't care.)
The books aren't overt about it because they aren't nearly as focused on Aragorn as the movies are, but we see clearly that Aragorn is happy in his current circumstances and views kingship as a burden. There is nothing kingship could give him that he wants. He's used to living as free as it's possible for a man to be, as a nomad following whims of the moment. Kingship is a cage - as Eowyn later notes.
In fact, in the books Aragorn proposes to Arwen and she accepts, but Elrond forbids them to marry until Aragorn is king of Gondor. And Aragorn does nothing. He loves Arwen, but he loves his freedom more. You could argue that he doesn't want to upset the political situation with things being kinda shaky in Middle Earth, but know who's on the throne as steward? Denethor.
|This guy is definitely a savvy political player; I foresee no problems at all.|
And while in the movies Boromir is all tetchy about GONDOR HAS NO KING; GONDOR NEEDS NO KING; EFF YOU ASSATHORN, in the books Boromir flat-out begs Aragorn to come fight for Gondor as its king. "I was not sent to beg any boon, but to seek only the meaning of a riddle," answered Boromir proudly. "Yet we are hard pressed, and the Sword of Elendil would be a help beyond our hope - if such a thing could indeed return out of the shadows of the past."
And later... "Mayhap the Sword-that-was-Broken may still stem the tide - if the hand that wields it has inherited not an heirloom only, but the sinews of the Kings of Men."
"Who can tell?" said Aragorn. "But we will put it to the test one day."
"May the day not be too long delayed," said Boromir. "For though I do not ask for aid, we need it. It would comfort us to know that others fought also with all the means that they have."
The ending in the book is not a happy one for Aragorn. He is forced to take up his right of kingship and do his best by the people of Gondor, no matter what he would rather his fate be (and, just to rub it in, Gondor does have peace under his reign as he sits on the throne - just like he claimed his fate wasn't). It's not a tragedy of course, but his happiness is qualified by the fact that he'd rather be somewhere else doing something else. BUT he's a good king doing right by his people, which takes precedence over personal happiness.
But what about divine right of kingship and that whole ickyness, you may ask? Does blood (either through ancestry or sometimes trial by combat) really justify kingship? Does it matter?
Well... Check back for part 3.