A frequent doubt expressed by adherents is if there is any significance to Mantra, Deity Yoga, etc., or if contemplation on Emptiness/Brahman itself was sufficient along the lines of Sūtrayāya/Jñāna path. The answer is not so black and white. For starters, the below excerpts from Jeffrey Hopkin’s translation of Tsongkhapa may be helpful.
Tantra means continuum, like a stream, of which there are three types: base, path and fruit. The base tantra is the person who is practicing. The base continuum is also the naturally abiding lineage, the element, the Tathagata essence. It is called the base because it is the basis of the activity of the path. The path tantras are the paths purifying that base. According to the lower tantras, these are the yogas with and without signs and, according to Highest Yoga Tantra, the stages of generation and completion that purify the defilements related with the suchness of the mind. The fruit tantra is the state of the effect, the Truth Body, complete extinguishment of all defilements as a Vajradhara. The three tantras – base, path and fruit – contain the subjects and meanings of all sets of tantras, and continuums of words and texts that express these subjects are called expressional word tantras that are divided into sets of groups.
The Perfection Vehicle is just the training in the altruistic mind of enlightenment and the six perfections; it does not clearly present any other mode of progress on the path. Mantra takes these as its basis but has other distinguishing paths. Since the Mantra Vehicle also has the practice of the altruistic mind of enlightenment and training in the six perfections, Tsongkhapa says that the Perfection Vehicle only has these paths.
There is no difference between the Perfection and Mantra vehicles with regard to the two objects of altruistic mind generation – the field of intent which is the welfare of other sentient beings and the object of observation which is one’s own attainment of Buddhahood. Trainees of Sutra and Mantra wish for the highest enlightenment for the sake of others and take cognizance of the same fruit, a Buddhahood that is an extinguishment of all faults and an endowment with all auspicious qualities.
There is also no difference in view, for Mantra does not explain a view of the middle way which exceeds that presented in the Perfection Vehicle by Nagarjuna. Even if there is a difference in view, this could not serve to differentiate the two vehicles since Chittamatra and Madhyamika, which have different views, are compatible in one vehicle.
The difference in vehicles must be determined through either wisdom or method. Because the wisdom cognizing emptiness is the mother common to all four sons – Hearer, Solitary Realizer, Bodhisattva, and Buddha Superiors – Hinayana and Mahayana are differentiated by way of the method, not by way of wisdom. For the same reason, the Perfection and Mantra Vehicles are differentiated by way of the method, not wisdom.
The Perfection Vehicle and the Mantra Vehicle also cannot be differentiated through practice of the six perfections. In Mantra it is necessary to train in giving, ethics, patience, and so forth during six sessions daily, dividing the day into six portions. Failure to do this is considered an infraction. Therefore, the presence or the absence of practicing the six perfections cannot differentiate the two vehicles.
The basic path for achieving a Buddha’s Form Body (Rupakaya) is the method – the altruistic mind of enlightenment induced by love and compassion. The basic path for achieving a Buddha’s Truth Body (Dharmakaya) is the wisdom cognizing emptiness. In Sutra and Mantra paths there is no difference with respect to these basic paths. Thus, from the viewpoint of the path that is practiced, its basis – altruistic mind generation – and its deeds – the six perfections including the wisdom cognizing emptiness – there is no difference.
The two vehicles cannot be differentiated by way of practitioners from the viewpoint of gradations in sharpness or dullness because if they were, the Perfection Vehicle itself would have to be divided into many vehicles. How, then, are the two vehicles differentiated?
Some say that the difference between Sutra and Mantra is that Mantra was taught for those who can use desire as an aid the path whereas the Perfection Vehicle was taught in order to tame beings within the context of separation from desire. This opinion is wrong because both the vehicles have modes of advancing on the path without having abandoned desire and both have modes of progress by cultivating paths to abandon desire.
The difference between the two vehicles must apply to one of the two meanings of ‘vehicle’: the means by which one proceeds or the fruit to which one proceeds. There is no difference in the fruit, Buddhahood; hence, the difference rests in the sense of ‘vehicle’ as the means by which one progresses to that fruit.
Mahayana is superior to Hinayana in terms of method, the altruistic aspiration to highest enlightenment for the sake of all sentient beings, and the division of Mahayana into a Perfection Vehicle and a Mantra Vehicle is also made by way of method. In general, the paths included within the factor of method are the means for achieving a Buddha’s Form Body whereas the paths included within the factor of wisdom are the means for achieving a Buddha’s Truth Body. To achieve a Truth Body, one needs to cultivate a path similar in aspect to a Truth Body, and both the Perfection and Mantra Vehicles have a path of wisdom in which one cultivates a similitude of a Buddha’s Truth Body: the cognition of emptiness in space-like meditative equipoise.
In order to achieve a Form Body, one needs to cultivate a path that is similar in aspect to a Buddha’s Form Body. Only Mantra has the special method for achieving this feat by cultivating paths that are similar in aspect to a Buddha’s Form Body. The presence of meditation that utilizes a similitude of a Form Body is the greatness of the Mantra method; such is not set form in Sutra.
In order to remove mental defilements, it is necessary to meditate on emptiness, but this is not a complete method for achieving Buddhahood because meditation on emptiness only removes the conception of inherent existence and all the afflictions that are based on it; other practices are needed in order to achieve the physical perfection of a Buddha. The complete method capable of bestowing Buddhahood quickly is the cultivation of a path of deity yoga in which the pride of being the deity of the effect state is established.
According to the Perfection Vehicle, in order for the wisdom cognizing emptiness to serve as an antidote to the obstructions to omniscience, it must be conjoined with altruistic mind generation and practice of the perfections. The vast methods such as giving, ethics, and patience help limitless sentient beings, and their imprint at Buddhahood is the achievement of Form Bodies that perform limitless altruistic activities. The wisdom penetrating the depth of the suchness of phenomena is the means for actualizing the non-conceptual wisdom consciousness of a Buddha. Thus, the special imprint of the collection of wisdom is the attainment of the Wisdom Truth Body coupled with the abandonment of all contaminations.
Neither a Truth Body nor a Form Body is attained singly because they both depend on the completion of these causal collections of method and wisdom. The two collections act as the co-operating cause and special cause of the Truth and Form Bodies. For example, an eye-consciousness is generated in dependence on three causes, an object, an eye sense, and a former moment of consciousness; the ability of an eye consciousness to apprehend color and shape rather than sound is the imprint of the eye sense; it’s being a conscious entity is the imprint of an immediately preceding moment of consciousness, and it’s being generated in the image of a particular object is the imprint of the object. Just as each of the three causes is said to have its own individual imprint in the generation of the eye-consciousness, the imprint of wisdom is a Truth Body and the imprint of the method is a Form Body.
Because the Perfection Vehicle sets forth a method for achieving the non-conceptual Wisdom Body of a Buddha and the Form Bodies affecting limitless maturations of other beings’ minds, it is said to have an unsurpassed method. However, in this path, the causes of the highest enlightenment are explained as only the six perfections. These are not sufficient because through cultivating causes such as giving, ethics, patience, and so forth – that are different in aspect from Form Bodies, the fruit – one cannot actualize the enlightenment of a Buddha. One would be attempting to actualize an effect that is different in aspect from the causes. The effect of Buddhahood, which has a nature of profundity, a Truth Body, and vastness, a Form Body adorned with the major and minor marks – in one undifferentiable entity, is achieved from causes that have a similar nature. Just as one meditates on the meaning of selflessness that is similar in aspect to a Truth Body, so one should cultivate paths of the vastness that are similar in aspect to a Form Body.
In the Mantra Vehicle, the ‘vast’ refers to the appearance of a divine body. There is a vastness at the time of the path – the cultivation of the vivid appearance of a divine body coupled with divine pride – and a vastness at the time of the fruit – an ultimate vastness that achieves the welfare of others. Deity yoga is ‘vast’ because deities who are qualified by emptiness and included within the factor of appearance, are inexhaustible, continual, limitless, and pure. Even though both pure and impure phenomena are qualified by emptiness, there is said to be a difference due to the phenomena qualified by it.
Mantra is distinguished from the Perfection Vehicle through its superior method for the achievement of a Form Body. Mere meditation on a divine form that is not related to meditation on emptiness is not sufficient because the branch of wisdom is not complete. Thus, the Body of a Buddha is attained through meditating on it. One should meditate on a divine body until its features appear clearly and steadily until it seems that one can touch it with one’s hand and can see it with one’s eye.
Someone might think that in the Perfection Vehicle, one cultivates a Buddha’s Form Body through meditation involving prayer petitions to attain such. However, if that were the case, one would not need to meditate on emptiness in order to attain a Truth Body; planting prayer petitions would be sufficient. Buddhahood is attained through non-dual yoga of the profound and the manifest; without it Buddhahood is impossible.