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?