Quote Originally Posted by d£v!l'$ ph0£n!x
i also think that sin has something to do with making the "dreams" have substance, as tidus and jecht travelled through sin to get to spira. though i am confused on how sin managed to get into the fayths dreams? and how auron was able to get a "lift" to the dream world on sin? (maybe it was a help from jecht's last shred of humanity). I still don't understand how jecht could get into the dreams though?
Actually, no. The Dreams of the Fayth naturally have substance; as with Aeons, the process of the Summoning gives them physical form. Sin is necessary, however, for residents of Dream Zanarkand to reach Spira, as Yu Yevon exerts a kind of overcontrol over Dream Zanarkand, whose residents are unaware of anything beyond the boundaries of their city anyway.

As the Dreaming is a physical event, like any Summoning, it takes place on Spira. Dream Zanarkand, then, is not another plane of existence/alternate dimension, but a physical location on Spira merely far removed from Bevelle, Luca, and the other places visited during the events of FFX. As such, all Sin needed to do to reach Dream Zanarkand was cross some undisclosed distance to reach the city; it was essentially the same thing as Sin moving toward any other population center on the planet.

Again, as Sin's journey to Dream Zanarkand was a physical event, bound up in physical travel, Auron had merely to ride along to also reach the place.

Auron: Don't make that face. Being dead has its advantages. I was able
to ride Sin and go to your Zanarkand.
Auron, an Unsent, was not bound to Spira in what might call the normal fashion, and thus was able to use Sin as a vehicle to the city. Jecht would have had no idea that Auron was even "along for the ride." Still exerting some small amount of control over Sin (also noted by Sin's preference for the Hymn of the Fayth), "Jecht" went to Dream Zanarkand, to see his son. There, Sin attacked the city because Sin is inherently destructive.

Like any resident of Dream Zanarkand, Jecht had real physical form. His "status" as a "Dream" merely meant taht his existence necessarily required the continued Dreaming of the Fayth. If it stopped, his link to Spira would be removed, and he would die. As this was the case, there was nothing that precluded him from giving himself to the creation of the Final Aeon, nor was there anything that prevented Braska's Final Aeon from being possessed by Yu Yevon and used as the "anchor" for a new Sin. Finally, as already noted, travelling to Dream Zanarkand was, really, an unextraordinary event.