Dual practice here isn't referring to the classic (western) philosophical debate of "mind body dualism". I'm talking about the Dual Practice (性命雙修) of mind and body in Taoist Neidan practice. On the surface, it looks simple: every mind-body exercise is supposed to train one's body and mind, isn't it? Like a tai-chi teacher will tell you he is teaching a mind-body exercise, and so will a modern Zen-meditation master, or for that matter modern Taoist master Mantak Chia too, with his sexual chi-kung, or anyone of the modern or new-age spiritualists who claimed to have an Eastern or Taoist orientation.
Taoist Neidan practice of Dual Practice(性命雙修) has been much more polemical. I shall try to explain what practice this classic concept supports and what it rejects in this post.
The important classic text Wuzhen pian 悟真篇 (Folios on Awakening to Immortality) had the following to say on this subject, and indeed making a strong (and poetic) message:
My translation (I have tried to keep its rhythm):
Yin's essence in Yang lacks in strength
Cultivate it alone shall lose all initial gains
Labor the body to channel chi is not Tao
Swallowing nature's essence are just insane.
Firstly, it is against meditation solely on one's third eye! The rationale behind is that without the physical training of "managing strong chi", one will eventually succumb to "outside pressure" during testing times (I shall go in depth into this area in some future posts).
Secondly, it is against practicing chi-kung like tai-chi! Chi practice without spiritual training cannot be called Tao. Moreover, chi generated NOT from one's inner-self is called "contaminated" chi (and therefore sexual chi-kung was being condemned)!
Thirdly, it is against taking essence of spirituality from nature outside one's body. It has to come from inside. In modern lingo, Neidan is all about psychology and psychological reality, rather than "breathing in more oxygen" only or taking "drugs" (nature or otherwise).
In addition to the above, a practitioner was supposed to be intellectually enlightened through studying the classic texts, like Tao Te Ching. This final point is often overlooked by practitioners and commentators (especially of Buddhist orientation) and wrongly accused these classic Neidan Taoists as "just technicians".
PS: Grandmaster of Center-group (中派) Li DaoChun (李道純) classified those "imperfect" practices into different grades. I find his classification very interested, and I shall post it here with my comments in future.