Trimurti (Sanskrit, “of three forms”) is the Hindu recognition oh the threefold required for creation and dissolution, hence especially the three interrelated divine manifestations; Brahma, Vishnu, and Shiva. Brahma embodies the rajas, the passion that creates; Vishnu embodies the sattva, the goodness which maintains balance; Shiva, the tamas, the fire which destroys. Another analysis is Vishnu creates while Brahma maintains equilibrium or order. As the importance of Brahma diminished, the “social” necessity of being (for this Trinity) required that Vishnu or especially Shiva being represented in the threefold activity. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 990