This veneration or deification of the Guru is found in most sects and assumes as extreme a form among the Saivas as among the Vaishnavas. The Saiva Siddhanta teaches that divine instruction can be received only from one who is both god and man, and that the true Guru is an incarnation of Siva. Thus the works of Manikka-Vacagar and Umapati speak of Siva coming to his devotees in the form of the Guru. In the sects that worship Krishna the Gurus are frequently called Gosain (Goswami).[436] Sometimes they are members of a particular family, as among the Vallabhacaryas. In other sects there is no hereditary principle and even a Sudra is eligible as Guru.
One other feature of Sectarian Hinduism must be mentioned. It may be described as Tantrism or, in one of its aspects, as the later Yoga and is a combination of practices and theories which have their roots in the old literature and began to form a connected doctrine at least as early as the eighth century A.D. Some of its principal ideas are as follows: (i) Letters and syllables (and also their written forms and diagrams) have a potent influence both for the human organism and for the universe. This idea is found in the early Upanishads[437] and is fully developed in the later Sectarian Upanishads. (ii) The human organism is a miniature copy of the universe.[438] It contains many lines or channels (nadi) along which the nerve force moves and also nervous centres distributed from the hips to the head, (iii) In the lowest centre resides a force identical with the force which creates the universe.[439] When by processes which are partly physical it is roused and made to ascend to the highest centre, emancipation and bliss are obtained. (iv) There is a mysterious connection between the process of cosmic evolution and sound, especially the sacred sound Om.
These ideas are developed most thoroughly in Saktist works, but are by no means peculiar to them. They are found in the Pancaratra and the later Puranas and have influenced almost all modern sects, although those which are based on emotional devotion are naturally less inclined to favour physical and magical means of obtaining salvation.