In the generation stage practices, as in all inner practices, the deities are depicted in union with consort. This is called yab yum. Yab is the male principle, the natural expression of appearance, and yum is the female principle, the natural empty wisdom nature of appearance. The actual offering of union, from a secret point of view, occurs when the deities’ secret centers are joined. The secret offering is always expressed by this union.
Even solitary deities incorporate the yab yum symbolism, though in a different fashion. The presence of the secret consort of a solitary deity may be symbolized by a trident held by the deity, or by the appearance of a tiny buddha, representing the head of the family to which the particular deity belongs, projecting from the deity’s crown.
A practitioner of dzog rim, the completion stage, will visualize his/her own form as the deity while engaging in practices that involve moving the energy up and down through the channels where the different experiences of bliss are achieved, moving the energy between the visualized bodies of the two deities. These practices are performed to experience great bliss, and when practicing them it is very important to always hold the pride of the deity and maintain awareness of the secret offering.
It is not exactly clear how Westerners got the idea that married couples, or, for that matter, any couple having a lot of desire for each other, could practice the Vajrayana techniques taken from tantric Buddhism or some other spiritual tradition. They try to visualize themselves as deities but then engage in an ordinary sexual act based on attachment/desire. They want an experience of something more blissful than ever before. This is one of the biggest mistakes a person can make. This activity does not even approximate the practices we are discussing. One who attempts tantric practices in this way, lacking the proper prerequisites and permission from the vajra guru, just accumulates causes for lower rebirth – even, perhaps, causes for the lowest possible rebirth, since this is to misuse and disrespect pure Dharma practice. Pure Dharma has nothing to do with ordinary sexual desire.
Since deities do not have desires, it is a grave error to visualize oneself as a deity to achieve purposes conceived by a desiring mind. When an anuyoga tsa lung practitioner becomes adept, gaining complete control over his or her channels, winds and essential fluids, he or she can perform extremely profound practices. A yogi or yogini who practices with a partner must not lose even one drop of essential fluid and must definitely be free of desire or attachment. To perform these secret practices, a practitioner must be on a very high level and must practice solely for the sake of sentient beings. When a practitioner arrives at this level of practice, it is very wonderful, but one must wait until the right time arrives.
The practices of union are the most secret for a number of reasons. For instance, one will not even hear of and certainly will not receive a transmission for these practices from anyone but one’s own guru, who can communicate them only through direct oral transmission. These practices are protected with secrecy because, of all desirable activities, human beings have the greatest desire for sex, and this desire causes them to misuse and misinterpret the practices. If human beings, motivated by sexual desire, attempt these most advanced techniques without being qualified, they will definitely suffer in lower rebirths. This is, in fact, one of the fastest ways to be born into the lower realms. These practices are kept secret to prevent their being misused.
You must understand that the Vajrayana practices are the swiftest of all Buddhist teachings and the most secret. They are protected ever so carefully by the protector deities (dharmapalas). If you misuse these practices, the dharmapalas create obstacles for you and your teachers. For instance, a potentially long life could be shortened. It is very important to refrain from running after teachers and receiving empowerments without first checking with your root teacher to see whether you are ready for them. Be very careful if you hear that some very secret empowerment is going to be given because if you get involved with something for which you are unprepared, the repercussions could be very serious. It could even ruin your path.