Various systems of thought and practice are mentioned
in classical Buddhist literature. Such systems are referred to as yanas or "vehicles."
There are, for instance, the various vehicles of humans and divine beings in
addition to the Buddhist vehicles: the vehicle of individual liberation (hinayana),
the vehicle of universal salvation (mahayana), and the vehicle of tantra (vajrayana).
In this context, vehicles of humans and divine beings refer to systems that
outline the essential training and methods for both fulfilling the major aspirations
of this life and, in addition, obtaining a favorable rebirth as either a human
or a divine being. Such systems emphasize the importance of maintaining an ethically
sound lifestyle--grounded in refraining from engaging in negative actions--since
leading a life of righteousness and good behavior is perceived to be the most
crucial factor for ensuring a favorable rebirth.
The Buddha also spoke of another category of vehicle, the Brahma Vehicle, comprising
principally those techniques of meditation that aim at achieving the highest
possible form of life within samsara, the karmically conditioned cycle of existence.
Such meditative techniques include, among other things, withdrawing the mind
from all external objects, which leads to a state of single-pointedness. The
meditative states experienced as a result of having generated single-pointedness
of mind are altered states of consciousness that, in terms of their phenomenological
aspects and also their mode of engagement with objects, closely correspond to
states of existence in the form and formless realms.
From a Buddhist point of view, all these diverse systems are worthy of respect
since they all have the potential to bring about great benefit to a large number
of sentient beings. However, this does not mean that all these systems are complete
in themselves in presenting a path leading to full liberation from suffering
and from the cycle of existence. Genuine freedom and liberation can only be
achieved when our fundamental ignorance, our habitual misapprehension of the
nature of reality, is totally overcome. This ignorance, which underlies all
our emotional and cognitive states, is the root factor that binds us to the
perpetual cycle of life and death in samsara. The system of thought and practice
that presents a complete path towards liberation from this bondage is called
the vehicle of the Buddha (buddhayana).
Within the Buddha's Vehicle there are two major systems of thought and practice:
the Individual Vehicle, or Hinayana, and the Universal Vehicle, or Mahayana.
The former includes the Theravada system, which is the predominant form of Buddhism
in many Asian countries, such as Sri Lanka, Thailand, Burma, Cambodia, and others.
In classical Buddhist literature, the Individual Vehicle is described as having
two main divisions: the Hearers' Vehicle and the Solitary Realizers' Vehicle.
A principal difference between the Individual Vehicle and the Universal Vehicle
exists in their views on the Buddhist doctrine of selflessness and the scope
of its application. The Individual Vehicle expounds the view of selflessness
only in relation to person or personal identity but not in relation to things
and events in general, whereas in the Universal Vehicle, the principle of selflessness
is not confined to the limited scope of the person but encompasses the entire
spectrum of existence, all phenomena. In other words, the Universal Vehicle
system understands selflessness as a universal principle. Interpreted in this
way, the principle of selflessness acquires greater profundity. According to
the Universal Vehicle teachings, it is only when a practitioner's experience
of selflessness is rooted in this universal interpretation that the experience
will bring about the elimination of the delusions and their underlying states
of ignorance. It is by eliminating these underlying states of ignorance that
we are able to cut off the root of samsara. Furthermore, a profound experience
of selflessness can also lead, ultimately, to full enlightenment, a state of
total freedom from the subtle imprints and the obstructive habitual tendencies
created by our misconception of the nature of reality. The system of thought
and practice which presents such a view of selflessness is called Mahayana,
the Universal Vehicle.
The Tantric Vehicle, or Vajrayana, which is considered by the Tibetan tradition
to be the highest vehicle, is included within the Universal Vehicle. In addition
to meditative practices for enhancing one's realization of emptiness and bodhicitta,
this system also includes certain advanced techniques for utilizing the various
elements of the physical body in one's meditative practice. Such feats are accomplished
on the basis of sophisticated yogic practices that principally involve mentally
penetrating the essential points within the body where the cakras, or energy
centers, are located. By means of this subtle and refined coordination of mind
and body, the practitioner is able to accelerate the process of getting at the
root of ignorance and completely overcoming its effects and imprints, a process
that culminates, finally, in the realization of full enlightenment. This feature--of
engaging in meditative practices involving the subtle coordination of both mental
and physiological elements within the practitioner--is unique to the Tantric
Vehicle.