 The Three  Vows[8]  is a polemical treatise, and it is Sapaṇ’s most controversial work. It is an assemblage of distinct doctrinal arguments directed against Sapaṇ’s Tibetan contemporaries, organized under the rubric of three sets of vows. The categories of vows refer to the three main categories of Buddhist theory and practice: (1) Disciples’ (śrāvaka) monastic vows, (2) Great Vehicle (mahāyāna) or bodhisattva vows, and (3) Mantra/Tantra vows. Before it ever reached Tibet, Buddhism in India had developed through these three forms, each with its own more-or-less distinct philosophical and ritual framework. Even as later systems became preeminent, however, earlier stages of Buddhist practice were kept, integrated into lower rungs in a complex  system.[9]  Yet although Buddhist intellectuals in India and Tibet took on this systematizing theoretical work, there was never a single institution capable of preventing innovation and experimentation in ritual and doctrine, and over the centuries numerous practices crossed the lines ideally set (often after the fact) between the categories.  Consequently, there were evident divergences between idealized systems and their practiced realities, and many conservative institutional leaders in Tibet during the later diffusion period (spyi dar) sought to reign in all errors, but especially those that upset the structured hierarchies of tantric Buddhism.