Saying that aliens created our galaxy is not a matter of faith; it is a theory because there is so little to go on, scientifically, to explain the origin of the universe.
The question then becomes, how were these aliens created?
If it is to be assumed that the aliens always existed, then why can we not assume that the galaxy always existed? And if it is to be argued that the question of the origin of the aliens is unanswerable, then why not save a step, and say that the origin of the galaxy is unanswerable?
