The exclusive preliminaries are Vajrayana practices such as receiving initiation (the best are Cakrasamvara or Hevajra since they are particularly associated with the six dharmas), keeping one's tantric pledges (samaya), Vajrasattva meditation and guru yoga. Tsongkhapa recommends that one practice generation stage meditation in preparation for the six yogas. According to Glenn Mullin,"it is obvious from Tsongkhapa' s tone that a number of his readers will have heard of practicing the Six Yogas without first having undergone sufficient training in the generation stage meditations." Tsongkhapa argues against this however. Tsongkhapa also writes that one must have an understanding of the doctrine of emptiness.