BTW, one thing that was interesting was the way that John Hurt, even after seeing his future, still decided he wanted to go through with it. Likewise, Tennant and Smith agreed with him. It was only Clara who forced him to think of a different option.
What I saw was that Hurt saw 10 and 11 refusing to allow UNIT to blow up London to save the world, and it was because they had once made a similar decision themselves. He saw that it was their regret over what he did that made them work all the harder never to allow that again. "How many worlds has their regret saved?" So, he reasoned that for them to be like that, he had to complete the circle and do the thing they regretted. He had to be the bad one, so that they could be as good as possible in response.
For 10 and 11, I agree that they were acting out of fellowship, of trying to lighten his burden once they realised that it had to be done. It was about accepting him as one of them, rather than dissociating from him as they had.
I've seen the episode about 4x now. I really think the Bad Wolf is there to change history. The War Doctor resolves 2x to use The Moment, and each time the Bad Wolf interrupts him.
Yes, I agree that the Moment stops him. Hurt thinks (and the audience thinks) that the reason she shows him that snippet of the future is so he'll see the regret of his future selves, as I explained above. What he and we eventually realize is that she
actually shows him that snippet of the future because it involved the 3D paintings, which gave him the idea of how to save Gallifrey. So yes, that was her ultimate reason - stop him from using the Moment, and save Gallifrey.
But that doesn't necessarily mean that she changed history by doing so.
From 11's point of view (and 11 is our POV character in this, since this is taking place in his era), this has all already happened. It's the past. This is what always happened - the Moment always convinced the Doctors to save Gallifery rather than destroy it, and that event always involved Hurt, 10 and 11 (and eventually the rest of them too) working together.
It's just that 11 didn't know that because it hadn't happened yet in his personal timeline, and Hurt and 10 didn't know it because their memories were wiped thanks to the 'out-of-sync timelines' maguffin.
So history wasn't changed - it just wasn't what we thought it was.
I think the 9th Doctor said he contemplated going back also but was unable to in the episode "Father's Day".
9's line in "Father's Day" was more that he
shouldn't do it, rather than that he
couldn't do it. I don't think the concept of a Time Lock - something that was actually
stopping him from changing anything regardless of his intention to or not - was introduced until 10's time.
But if we assume that 9 also knew about the time lock, as surely he must, then presumably he thought of the events of the Time War, including the destruction of Gallifrey, as a Fixed Point. An event in time and space that has happened, will happen, and must always happen because it's an integral part of the fabric of existence. Something that you can't change because if you do the universe falls apart.
That was the theme of "Father' Day" - that there are some things you can't change, no matter how much you may want to. It was also the theme of "Parting of the Ways" - that you
can change things in your mind, even if not in reality, by making a different decision when faced with the same circumstances. You may not be able to change the Fixed Point, but you can make up for it by doing something different next time.
Then we come to "Wedding of River Song," where we learn that sometimes a Fixed Point is not what you think it is. 11 thought that he had to die at Lake Silencio, that nothing could change that. Everybody in history thought the same. But that wasn't what the Fixed Point actually was - it was only that everybody
thought he died, not that he
actually died. It looked like he changed a Fixed Point against all the rules, but it was actually just that he misunderstood what the Fixed Point was. History didn't change, just our understanding of it.
Then you've got things like "The Fires of Pompeii" or "The Waters of Mars," where everything 10 does to stay out of the way of history and not change anything only ends up with him involved in events all the more, and his eventual understanding that this is always the way it was. Even when he does manage to tweak a couple of details, they snap back into place against his will. History
refuses to be changed, not when there's a Fixed Point involved.
All of those come together in "Day of the Doctor." He has the opportunity to change his mind when faced with the same circumstances again. We realise that what actually happened is not what we thought happened. And history resolves itself around the paradox by simply making the Doctor forget.
.