* MAJOR SPOILERS IN THIS QUESTION!!!!
John Vattic has precognative visions that show whether someone is going to die or not. Why does Present John Vattic never show any indication that he is receiving precognative visions at any point during the present sections of the game until the reveal? In fact, present John continues to disbelieve of psychic powers for most of the game, until he gets them himself, despite getting visions of people dying and then preventing said deaths from happening left and right. The reason this is important is that it fails to show, or at least make it obvious why the visions have any effect on present John's actions.
If the visions don't effect him, then the people who are supposed to die just die. If they do, then why is he doing pretty much the same thing he would have been doing in the present that he probably would have been doing if he never even had the visions, and why does he keep denying psychic powers?
Also, those visions only show the FACT that somebody is going to die, most of the time they don't show how, so even if they DO effect him despite his denials, then how could he possibly know how to save them? Last, why it even possible to fail those precognative parts? If they're precognative visions they should just be like watching a movie instead of something that future John could possibly fail.
** First, I now have a headache. Secondly, it's likely that John's psychic powers (or what little of them Zener children had awakened by the time he showed up at the military base) have so completely twisted his thought process out of shape that he's gotten the past, present and future confused. As for why he doesn't talk about his visions, he's a skeptic anyway, and more than a little bit egotistical: it's natural he doesn't want to talk about it- remember when he refuses to believe in psychic powers while ''talking to an astral projection,'' after having seen it possess Colonel Starke at least twice?\\
Furthermore, he actually does talk about his visions later in the game, when he starts referring to things that occurred in his visions. Given that most of the visions seem to kick off following lulls in the action, it's possible that the visions manifest themselves while present John is asleep or unconscious- at least until the team reaches Dubrensk- so he can just dismiss them as dreams until then; after that, he's just zoning out. As for how he knows how to save the others, I think the visions at least put him on edge and keep him alert for when the inevitable disaster occurs (in much the same way as they would put the player on alert). \\
Last but not least, as for how it's possible to fail, John is exploring ''possible futures'', which include the ones where he buggers it all up. This is why he gets to return to the checkpoint instead of being shown an Enigma ending; I'd suspect that this also connects to the reason why he finally stops having visions of the BadFuture and has the psychic breakdown that occurs in the final chapter of the game- he was faced with a no-win scenario.\