During recent years the Ved~ntic doctrine of illusory appearance (vivarta) and the problems connected with the idea of illusory change, causation and discontinuity have received a considerable amount of attention. In the course of this work several schools of thought -notably the early Advaitic and the Buddhist -have been taken into account; but the Indian linguists and philosophers of grammar appear to have been somewhat neglected, although, as has been noted, Bhartrhari, the grammarian author of the VdkyapadTya, is perhaps the first to use the term vivartate in an illusionistic context 1 and despite the fact that the importance of Patafijali's Mahdbhd.sya for the history of Indian philosophy was recognised long ago. ~ It will be recalled that the treatises that deal chiefly with the phonological features of words in combination in the Vedic sam. hit,s with regard to their form in isolation thus safeguarding the form and recitation of these texts, the Pfftti~tkhyas, describe the change in sam. dhi of one sound into another, for example i > y before a vowel. This linguistic process is normally expressed by most of the Pr~ti~khyas in a corresponding manner. The .~gvedaprdtiddkhya rules: amum iti tadbhdvam uktam, yathdntaram (1.56), "(One should understand that) the expression 'this to that' means becoming that, with reference to the sound which (in its relation) stands nearest to it". 3 Elsewhere in the RVPr. the term vikdra "modification" is used, e.g. in 2.5 where mention is made of the vikdragdstra, that is of the rule of the modification of sounds, and in 11.44 where euphonic modifications in the tcramapdt.ha are described. The same type of statement is to be found in the Taittir[yaprdti~akhya where we read atl~ vikdrasya (1.28), "am [i.e. the accusative] makes the name of a product