The teachings of the Buddha are classified as either sutras or tantras, both of which exist as written scriptures, recorded centuries after they were taught. Sutras were taught publicly in dialogue form and have always been widely available. There are various types of tantric texts, including medical and astrological tantras, as well as the root texts of Vajrayana meditation practice, such as the Kalachakra Tantra. The Buddha conferred the tantras while assuming the form of various deities. He taught them secretly to individuals or groups because only those who had a certain background and education were prepared to integrate them into their practice.
Tantra is the core of Vajrayana Buddhism which has been widely practiced in Tibet and Mongolia for more than 1,300 years. Vajrayana (the “diamond path,” also known as Tantrayana and Mantrayana) is said to be the most direct path to transformation and enlightenment through tantric practice.
Kalachakra is one thousands of tantras taught by the Buddha. At the center of each tantra is a deity, which is regarded as a manifestation of a particular aspect of Buddha mind. Rather than gods to be adored, the deities are perceived as personified states of mind, to be attained and mastered as one progresses on the path toward enlightenment.
There is no tantra without a deity; likewise, each deity embodies a tantra. With each deity thus representing an aspect of Buddha mind, each tantra discloses methods for realizing the awakened state of the deity. Thus each Buddhist Tantra has the name of a deity associated with it, for example Kalachakra Tantra, Guhyasamaja Tantra, Mahavairocana Tantra, Tara Tantra, Hevajra Tantra and so on.
Tantric Buddhism, the mind is seen as the central source of being. It is the stream of consciousness which connects the individual to his or her past and future. This can be observed within the actions of this life alone or, according to the principle of reincarnation, in the actions of past and future lives. The mind is a repository of these actions and the impressions they make, known altogether as karma, the law of cause and effect which carries over from lifetime to lifetime.
At the center of tantric practice is the subtle mind, which from the Buddhist perspective resides at the heart center (not to be confused with the physical heart) and is the source of our vitality, compassion, and wisdom. This is significantly different from the Western viewpoint, which regards the mind as a function of the brain, with an emphasis on deductive reasoning. The tantric mind holds both the relative truth and the absolute or ultimate truth.
Thus Buddhist tantra is not only the teaching but also a guide to achieving and abiding within the enlightened state of being. It is also the transmission of its teachings, which are passed from generation to generation by lineage holders who are empowered to do so.