Khenpo Tsultrim Lodro
The main criterion for attaining realisation is to have faith in the Vajra Master and Vajrayana. Then, one needs to purify the karmic obscurations. At the very least, these obscurations need to lessened by some degree to the point where all the very gross and heavy negative karmas are purified. The third requirement is to have sufficient merits. The last requirement is to have a teacher’s guidance.
If you wish to realize the Buddha nature, you need to practice Dzogchen or Mahamudra and other practices like these. If you have a very keen faculty or a high level of mind then even a very busy householder can attain realisation. You can even gain realisation in the public bus while you are on the way to work. However, if you do not have such a capacity, then even if you are very studious and memorize all the scriptures without leaving a single word out, it doesn’t help much. If you do not have faith, you will not gain realisation your entire life.
(Note: Therefore, it is important to build up the capacity and faith through the preliminaries.)
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Tantra tells us that before the wisdom of realising emptiness has arisen, we need to use the preliminary practices (ngondro) to cultivate renunciation and Bodhichitta. We need to practice Vajrasattva to purify our defilements and offer the mandala to accumulate merits. When the conducive conditions are gathered and the obstructive conditions are cleared, you practice Guru Yoga and attain realisation through the Guru’s blessings. After realisation, all the views and contemplations of Madhyamika are no longer needed. One can dispel the two obscurations solely through the wisdom of realising emptiness, revealing the clear light luminosity of the Dharmadhatu.
(About Khenpo Tsultrim Lodro: Khenpo is the vice dean of the Larung Gar Monastic University. It is said the Khenpo is the emanation of Longchenpa.