In my previous posts I discussed the theory of dual (corporeal) sexual practice in Tantra using the mythical history of Lady Yeshe Tsogyel as illustrative example. Needless to say, this is my own interpretation only, learned scholars of Tibetan Buddhism would likely to consider my interpretation a bit too layman-like and superficial, if not out-right wrong. Anyway, my analysis is that there is indeed a theological reason behind dual sexual practice in Tibetan Buddhism given its theology as evidenced in the book Sky Dancer.
Before I go to compare it with Taoist dual sexual practice, it is interesting to note the similarities in their ideas of sexual sublimation， for example:
1. On the reverse procedure of sublimation:
TB: About the body: do not let it slip into old habits
Or you will become like ordinary men and women;
T: Goes the usual route, man will be created (goes the reverse route, Immortal will one become) 順則成人，逆则成仙
2. On against erotic thoughts:
TB: Preserve constant cognition of the primal purity of experience; Protect the samaya like your body and life,
For if it is broken there is no authority to restore it.
T: Erotic thoughts will damage the clarity of the Water, and false elixir will be produced. 先後清濁，即水源之辨。真丹、幻丹之所由別也！
The concept of Offering doesn't form part of Taoist Neidan's philosophy. The Primodial chi (先天真一之气) is to be cultivated for enlightenment, which is also the same source for procreation! As such, dual (corporeal) sexual practice doesn't belong to the theory of Taoist Neidan practice. And such practice is therefore rightfully classified as sexual chi-kung rather than Taoist Neidan. And with this conclusion, I rest my case here.