I'd like to address the 'Lifestream Theory' on how Cloud arrives in Ivalice if I may. I find it highly unlikely that this is the explanation for Cloud's arrival.

First, there is no evidence that the Lifestream is a gateway for time travel in FFVII. Unless I am mistaken, the Lifestream is the coalescence of all deceased life on the Planet, which in turn maintains a sense of homeostasis on the Planet, maintaining balance and integrity. This is why the Lifestream aided (or strove against) Holy at the ending of FFVII to stop the imminent destruction of the Planet. Basically, the Lifestream is a kind of glue that keeps the Planet together in some respects. Yes, physical beings can make contact with the Lifestream, and be inadvertantly 'swept up' in it. However, following the logic supplied from FFVII, Lifestreams probably exist in every world within the Universe (that caters life) and they are probably governed by a set of physical laws. And so, the Lifestream in question that exists on the Planet where FFVII occurs is restricted to that particular planet. The events that occur in FFT are certainly not occuring simultaneously as the events of FFVII unless it is a different planet. So...in order for the Lifestream to act as a vehicle for Cloud to travel from the Planet to Ivalice, and vice versa, the Lifestream must be able to either cross over between worlds, or be able to access different time periods.

Secondly, if the Lifestream were to 'cross-over' to another world, say, the one where Ivalice exists, that would require tremendous energy. This energy loss could *possibly* cause damage to the Planet. Remember when Bugenhagen shows the animation of the Planet dying as a consequence of the Lifestream being drained away by Shinra? A similar fate could come to pass if the Lifestream leapt from one planet to another. It all depends on distance of course, but the farther the planet in question is away, the more energy loss would occur. And also, what would act as a catalyst for this event to occur? Cloud certainly didn't expect to end up in Ivalice, indicating that the event was either an accident or a terrible mistake. And what purpose would the Lifestream have in transporting Cloud to Ivalice? Ramza & Co. would have defeated Ajora and the Zodiac Braves without Cloud.

Thirdly, if the Lifestream could in fact transport a living being back in time, then why doesn't Cloud travel back in time and save Aeris?

*The best thing that you guys have going for this theory is that Aeris somehow made it to Ivalice...alive. I can't really explain that.

Just my two cents.