In [The Avengers: Age Of Ultron](tag:293035), the new Avenger, The Vision is able to lift Thor's mighty hammer Mjolnir. Captain America, along with the rest of the team, are unable to do so. Many have speculated that this is because The Vision is truly "worthy" and that Cap, Hawkeye, Stark, and Rhoady are not. I'm here to offer a new perspective and theory.
At this point we all clearly understand that the Marvel Cinematic Universe and the Marvel Comic Universe story lines are not consistent with each other. Joss Whedon, Kevin Feige, Jon Favreau, James Gunn, the Russo Bro's and the rest of the MCU Team have been on record saying that they are more or less using the comics as a reference point, and that they would be creative with the stories to create a unique Marvel Universe.
With that said, what if the reason The Vision could lift Mjolnir is simply because Thor's might hammer contains an Infinity Stone. Specifically the Soul Gem. And by being in possession of an Infinity Stone, you are able to wield other items containing an Infinity Stone. So by having the Mind Gem lodged in his forehead, Vision is able to lift and swing Mjolnir.
But what reasons do we have to believe Mjolnir contains an Infinity Stone? And Why The Soul Gem?
In Thor (2011) Odin, King of Asgard says the following;
"Thor, Odinson. My heir, my first born, so long entrusted with the mighty hammer Mjolnir. Forged in the heart of a dying star. Its power has no equal, as a weapon to destroy or as a tool to build. 'Tis a fit companion for a king."
The key line of the quote is "Forged in the heart of a dying star". This sounds very similar to the creation of the the Infinity Stones as described by The Collector in Guardians of the Galaxy.
Also, the line "Its power has no equal, as a weapon to destroy or as a tool to build". This sounds very similar to ones "Soul". A good soul can build greatness amongst its presence, but an evil or bad soul can cause destruction and terror.
When Odin banishes Thor and strips him of Mjolnir and his mighty power he says the following;
"Whosoever holds this hammer, if he be worthy, shall possess the power of THOR!"
That line pretty directly addresses that whatever is inside Mjolnir is responsive to ones "Soul". That is how it is able to deem "worthiness". So clearly the Soul Gem could be contained within Thor's hammer.
We know Odin is in possession of a Tesseract and an Infinity Gauntlet, so it is entirely possible to believe he was also in possession of the Soul Gem. Just like the Chitauri did with the Mind Gem and Loki's scepter, Odin may have done the same with Mjolnir and the Soul Gem. Containing an Infinity Stone inside a weapon seems like a reasonable and effective way to keep it out of Thanos' grasp.