Thank you for taking the time to answer my many questions, Namdrol.
Namdrol wrote:Plus, you have to understand, that this experience is what is introduced during empowerment, and further, since the channels have been purified, the movements of winds are more subtle; and hence the mind is more subtle; hence the emptiness realization is more profound and more rapid.
Is this why Buddhahood is said to be immediately possible in a lifetime in tantra? By virtue of the emptiness realization being more profound and rapid than in sūtra? How does the accumulation of merit factor into this? Tantric methods produce more merit?
Tantric methods produce more merit, more rapidly using special methods such as mandala offerings. Typically, the merit and wisdom accumulation sections of any anuttarayoga tantra sadhana are theoretically capable of producing the equivalent of three incalculable eons worth of the two accumulations in a single session. Your individual milage may vary.
Monastics are prohibited from sexual intercourse, but is the visualization of the activity equally as efficacious as the physical act? I understand Je Tsong Khapa decided to forego the act of coupling out of concern for disciples and achieved his liberation in bardo.
There is very little agreement on this issue among Tibetan lineages. There is also considerable disagreement about this issue in Indian sources. So this is a difficult point. Some masters assert that a monastic may use a consort having achieved the path of seeing. Other masters assert that it is fine for them to use a consort upon attaining patience on the path of application.
However, auto-erotic techniques may also be applied in absence of a consort. This is the usual mode of practice for single practitioners and monastics. For example, Vajraghantapada (a bhikṣu) asserts, in connection with the practice of Cakrasamvara, that while sexual misconduct is not a practice recommended in the tantras (because you must protect the bodies of others, etc.), non-celibate conduct (abrahmacarya) is.
Jeff's (Jnana) posts on this subject exhibit a specifically Gampopa/Kagyu POV on this issue.
In general, the Sakya school and Nyingma schools place much more importance on erotic practices than do the Kagyus. However, in the Nyingma school they are not generally considered indispensable for awakening in this lifetime. In most of the Tantric lineages within Sakya, they are considered indispensable for awakening in this lifetime. The exception to this would be the oral instructions of Naropa's Khechari -- where a type of pranāyāma practice is said to result in a state of bliss equivalent to the bliss of sexual congress and therefore obviates the need for a consort (also partially accounting, I feel, for the reason the Naropa Khechari instructions have attained the popularity they have). Thus, there can be differences between specific oral instruction lineages as well. This is why the instruction of a properly qualified guru is key on this point -- since there are so many lineages, and differences in practices even of the same deity in different instruction lineages.
The Kagyus and Gelugs have skeptical attitudes towards erotic practice grounded in Kadampa opinions. However, of the latter two, the Gelugs also generally maintain that erotic practices are indispensable for awakening in this lifetime.
Is the amount of merit a practitioner has from past lives taken into account when it is said that Buddhahood is possible in one life using tantric methods?
No. The statement that someone could achieve complete buddhahood in one lifetime through Vajrayāna methods refers to a beginner on the Mahāyāna path.