The Puranas teach Time is a form of Vishnu; it is used to measure the duration of existence for all sentient and insentient beings. However, there are beings which are not sentient nor insentient, and beings which are both sentient and insentient. For such beings, existence cannot be measured by Time. Vishnu is one of these beings - for what meaning does time hold to Time? Narayana, which is without form, is also one of these beings, for what meaning does a form (of Time, or any other thing) have to what is formless?
When Brahma, another being for whom Time has no bearing, woke to discover the void - in this moment observation could encompass only the observer. Then differentiation was made between void and non-void. By logic, one can infer what is solid by observing a liquid, as one could infer the land from the sea, Brahma, by supreme logic, inferred the entirety of existence from the void; for Brahma understood what was the void, and what was the non-void, what was neither void nor non-void, and what was both void and non-void - even as one might, by logic, from understanding liquid and solid, discern air, and the other forms of matter.
It was in this process that Brahma assumed new form after new form: first, Brahma was a fish in the water, and in swimming, discovered the limits of liquid, understanding from liquid solid and air, and other forms of matter. Then, becoming an amphibious turtle, Brahma explored the land; in exploring land, Brahma became a boar. It was as a boar that Brahma inferred the Vedas, and by this Dharma comprehended, defined and preserved all that had been inferred.
Upon Brahma declaring the Dharma, all that had been inferred by Brahma became able to observe Brahma, and bowing in adoration, declared Brahma to be God.