The post-Vedic texts of Hinduism offer multiple theories of cosmogony, many involving Brahma. These include "Sarga" (primary creation of universe) and "Visarga" (secondary creation), ideas related to the Indian thought that there are two levels of reality, one primary that is unchanging (metaphysical) and other secondary that is always changing (empirical), and that all observed reality of the latter is in an endless repeating cycle of existence, that cosmos and life we experience is continually created, evolved, dissolved and then re-created. The primary creator is extensively discussed in Vedic cosmogonies with "Brahman" or "Purusha" or "Devi" among the terms used for the primary creator, while the Vedic and post-Vedic texts name different gods and goddesses as secondary creators (often Brahma in post-Vedic texts), and in some cases a different god or goddess is the secondary creator at the start of each cosmic cycle ("kalpa", aeon).