The latest episode of Agents of S.H.I.E.L.D., "The Force of Gravity," left the S.H.I.E.L.D. team faced with an impossible dilemma; should they save Phil Coulson, or should they save the world? Season 5 has revisited a number of key plot points from the last five seasons of Agents of S.H.I.E.L.D., most recently the Centipede Serum. Introduced back in season 1, it seems the Centipede Serum can be used to save Phil Coulson. Or, alternatively, it can be used to kill Graviton. But S.H.I.E.L.D. did too good a job taking down Hydra, and there's only one sample of the serum left. Will S.H.I.E.L.D. choose to save Coulson, or to save the world?
There's a certain irony to this plot twist. Future Yo-Yo warned her present-day self that S.H.I.E.L.D.'s efforts to save Coulson would lead to the destruction of the planet. As a result, Yo-Yo believes Coulson simply has to die, and she and Quake literally came to blows over it. But if Daisy hadn't been trying to save her father-figure, S.H.I.E.L.D. wouldn't have a single sample of the Serum. If S.H.I.E.L.D. do indeed save the world and break the time loop, it's precisely because they chose to try to save Coulson.
Part of the problem is that temporal mechanics are hardly simple, and the S.H.I.E.L.D. team are new to traveling through time. Future Yo-Yo admitted that every word she said to her past self was part of the time loop; however hard she tried, she just couldn't focus enough to say anything different. That means her words should hardly be taken as Gospel -she might as well be the voice of the time loop. Meanwhile, "The Force of Gravity" saw Fitz come up with an audacious proposal - one that would potentially break the loop once and for all.
Can Time Be Changed?
Agents of S.H.I.E.L.D. has toyed with two different theories as regards the nature of time. In the season 3 episode "Spacetime," Fitz argued that the future is, to an extent, predetermined. Once you have experienced the future, you know exactly what will come to pass, and your destiny becomes fixed and unalterable. He's propounded this same theory through the bulk of season 5, albeit inconsistently. So far, the entire time loop is happening exactly as Robin prophesied, and the world's fate seems to be sealed.
Deke, however, has introduced a second theory: the Multiverse Theory. In this theory, there are crucial moments that create parallel dimensions, timelines where events played out differently. He believes, therefore, that somewhere in the loop there's a crucial decision that acts as a branch in the road. One choice can save the world, averting the timeline in which Earth has been destroyed. Though Deke doesn't know it, the MCU is clearly taking the Multiverse model. In Avengers: Infinity War, Doctor Strange uses the Time Stone to peer into millions of different futures, in order to determine which one Thanos would be defeated in. That simply wouldn't be possible if time were fixed, thus proving the Multiverse theory for the MCU.
The task facing S.H.I.E.L.D. is, in theory, a simple one: identify the point where the timelines branch out, and choose the branch that saves the world. In reality, of course, it's far more complicated than that, since S.H.I.E.L.D. has no way of knowing which decision is the crucial one. "The Force of Gravity" sees Fitz suggest one simple way - rather than try to save Coulson, what would happen if S.H.I.E.L.D. succeeded? Coulson wasn't part of that horrific dystopian future, so adding him into the mix would break the loop. Assuming Fitz is right, is it possible to save Coulson and save the world?