The Doors of Truth is the source of alchemical knowledge and the entrance to God's domain, where no mortals are meant to tread. In many ancient traditions, it was said that a disciple in his 'path to wisdom' would go through training and a sort of 'purifying' of himself to be able to pass through that 'portal' which symbolizes the acquirement of wisdom and a certain degree as a "Master", having access to knowledge about the 'mysteries of the universe'. So, metaphorically, the Gate represents the 'passage' from one condition to another, a twilight zone. In FMA, whoever attempts to perform a certain transmutation that is considered to be something of "God's access" (as a human transmutation), that alchemist is taken to that portal, where he can have access to a certain degree of knowledge fr