I was just looking at this gifset and decided it would be better to put my thoughts into my own post rather than tag them onto the end of the set and annoy people with my comments.
We tend to see Sherlock as a loose canon and John as the one who ‘keeps him right’ or ‘conducts his light’. True. John is an amplifier for Sherlock’s good qualities; his brilliance, his charm, his feelings.
But in that scene, we see how John is the loose canon, and Sherlock is the one who grounds him. Not only that, but Sherlock is aware that this is his purpose. He knows exactly what he has done for John in the past (helping him overcome his limp, giving him the kind of life he craves, etc).
John is riled up. He’s ready to burst. And Sherlock says ‘be calm and answer me’. He does something that Mary hasn’t been able to thus far which is bring John back down from that aggressive rage. She couldn’t do it in the restaurant in TEH, nor at the beginning of HLV when John runs off to go and beat up some junkies. Sherlock really, truly knows John and understands how to treat him. Earlier on in that scene, John threatened to knock Sherlock out because he thought Sherlock was taking the piss. He threatened to hit his best friend who was shot only a week before and should technically still be in the hospital. John is fucking dangerous and definitely not in his right mind. But Sherlock doesn’t cower, or threaten him back. He just tells John to be calm and think things through. Sherlock doesn’t get frustrated when John gives the wrong answers. He just repeats the question and waits. Because he knows that John understands what he’s saying, it’s just that his anger is in the way, it won’t let him approach this sensibly.
This dependency on Sherlock for clarity is further evidenced by the fact that John asks Sherlock, ‘But why is she like that?’. Sherlock is John’s font of reason and logic, and in a situation that he can’t comprehend he has to ask his friend why his own wife is ‘like that’ (what he’s really asking is ‘why is she like us?’, or perhaps more specifically ‘why is she like you?’, meaning Sherlock. To which the answer ‘because you chose her’ kind of breaks my heart).
The point I’m trying to make, and that I think series 3 is trying to make, is that this scene perfectly illustrates how much we’ve focussed on John’s effect on Sherlock in the past, but in fact Sherlock has been just as vital to John. I dread to think what John must have been like during those 2 years alone.