Heroism is an interesting thing. What makes one person good can be drastically different than what makes another person good. There are a multitude of ways to embody goodness, just as there are many ways to embody evil. But we don’t often talk about the subtleties of goodness the way we do with villainy. You’re either good or you’re not.
Which brings me to a question: what specifically makes Thor good enough to hoist Mjolnir?
Spoilers for one released scene from Avengers: Age of Ultron discussed below.
In the comics, Mjolnir has switched allegiances before, been hefted by others, even been taken outright from the god of thunder. While Odin is meant to have absolute control over the hammer, that is not always the case; the current storyline shows Odin unable to control Mjolnir, resulting in another having to pick up the hammer and wield the power of Thor. Previously, Captain America has managed to pick up the hammer, as has Storm, and of course, Beta Ray Bill. Outside of central continuity (in alternate realities and the like), we have an even wider gamut, from Loki to Rogue to Jane Foster to Black Widow to Superman to Wonder Woman.
A teaser scene from Avengers: Age of Ultron shows most of the team having a go at picking up Mjolnir at a Tower party. No one pulls if off, but Steve Rogers does manage to budge the thing, causing Thor to look a little nervous. Widow opts out of the game, which has led to many a fan crying for a scene where Widow just picks the thing up mid-battle, without giving it a thought. (Which you cannot deny would be massively cool.)
It does beg the question of how Mjolnir itself evaluates worthiness. In both the comics and the films, Thor is capable of using the hammer even when he’s being… well, kind of an asshole. Odin rips Thor’s powers from him with the intent of teaching his son important lessons, but he has no control over the crowning moment in the Thor film, for example—when it’s clear Thor has learned, Mjolnir returns to him. But if Mjolnir has that power, shouldn’t it be able to tell that Thor was unworthy in the first place?
Perhaps not. Perhaps worthiness is all a state of mind.
After all, wouldn’t we assume Captain America should be able to lift the hammer? He’s a pretty darn good guy. He puts others ahead of himself every step of the way. He believes in total equality and holding governments accountable to their citizens and making sure the masses aren’t ruled by fear. How is Steve Rogers Good different from Tony Stark Good different from Black Widow Good different from Thor Good?
And what if the point is simply that Thor always means to do good?
Because if there’s anything that separates Thor from everyone else as a character, that is probably it. Thor is guileless—he has not one cynical bone in his body. Even when he commits acts that are questionable, it’s always with the noblest of desires. That’s what being Asgard’s greatest warrior is all about. Thor may not be pure of action, but he is pure of intention. That is the center of the conflict that we see in Thor all the time. He thinks he’s doing the right thing when he’s just blustering around hitting people (and just as often making the situation worse). You’d think that wouldn’t make him worthy of such a powerful weapon, but it seems that Thor’s belief that he’s doing good amounts to something.
It might be one of the things that makes him such a charming hero. It’s easier to relate to the desire to do right than the constant ability to be a pinnacle of humanity (or Asgardian..ity). Thor possesses a refreshing lack of cynicism about his purpose and deeds. And that lack is something that the majority of the Avengers lack; as a crew, they are about as self-deprecating, suspicious, and disappointed as your average human being who’s come into contact with that nastier side of humanity. Their momentum to do right is still genuine, but they’re aware that what constitutes rightness is rarely a simple question.
It also might make sense of why Steve Rogers in the movies can’t heft Mjolnir, but Steve Rogers in the comics can. Captain America is a bit more white bread and gung-ho on paper. In the films, Chris Evans plays Cap with a solid moral core, but with far more misgivings about the intentions of others. You can’t exactly blame him for it, either—working for SHIELD only to find out that the whole caboodle was secretly being driven by the very group he spent WWII trying to stop is… well, it’s bound to make all those solid lines he’s good at drawing seem mighty permeable, even to him.
Thor and Mjolnir form a sort of Catch-22 in this way, perhaps. It is likely that the only reason the thunder god is unable to pick up the hammer in the Thor film is because he is aware that Odin finds him unworthy, and he values his father’s opinion in this matter above all. But in The Avengers, we see the big fella mulling it over in a field after getting dropped out of the helicarrier. He looks down at the hammer, then to his own hand, wondering all over again; if a sibling he loved was willing to murder him without a thought, it stands to reason that you might reevaluate yourself. But in the end, he picks up Mjolnir and rejoins the fight. The ability to lift Mjolnir becomes a restorative in itself—by being able to pick it up, Thor’s confidence is forever renewed.
In the end, it’s easy to argue that Mjolnir is not the ultimate arbiter of goodness, not by a longshot. It’s simply a tool that is designed to respond to those who lack the cynicism and doubt so omnipresent in our consciences. Thor’s ability to believe he does well enough to deserve such a weapon doesn’t make him the greatest hero of all—but it does make him a very special kind of good. And that unsubtlety of character is part of what makes him such a lovable oaf in the first place.