The collation order of Brahmi is believed to have been the same as most of its descendant scripts, one based on Shiksha, the traditional Vedic theory of Sanskrit phonology. This begins the list of characters with the initial vowels (starting with a), then lists a subset of the consonants in five phonetically-related groups of five called vargas, and ends with four liquids, three sibilants, and a spirant. Thomas Trautmann attributes much of the popularity of the Brahmic script family to this "splendidly reasoned" system of arrangement.[29]