Introductory Commentary by the XIVth Dalai Lama to the Tibetan Book of the Dead

The question of whether or not there exists a continuity of consciousness after death has been an important aspect of philosophical reflection and debate from ancient Indian times to the present.  When considering these matters from a Buddhist point of view, however, we have to bear in mind that the understanding of the nature of continuity of consciousness and the understanding of the nature of the 'I' or 'self' are closely interlinked.  Therefore, let us first look at what it is that can be said to constitute a person.
According to Buddhist classical literature, a person can be seen as possessing five interrelated aggregates, technically known as the five psycho-physical aggregates.  These are the aggregate of consciousness, the aggregate of form (which includes our physical body and senses), the aggregate of feeling, the aggregate of discrimination, and the aggregate of motivational tendencies.  That is to say, there is our body, the physical world and our five senses, and there are the various processes of mental activity, our motivational tendencies, our labelling of and discrimination between objects, our feelings, and the underlying awareness or consciousness.
Among the ancient schools of thought, which accepted the notion of continuity of consciousness, there were several non-Buddhist philosophical schools which regarded the entity, the 'I' or 'self', which migrated from existence to existence as being unitary and permanent.  They also suggested that this 'self' was autonomous in its relationship to the psycho-physical components that constitute a person.  In other words they believed or posited that there is an essence or 'soul' of the person, which exists independently from the body and the mind of the person.
However, Buddhist philosophy does not accept the existence of such an independent, autonomous entity.  In the Buddhist view, the self or the person is understood in terms of a dynamic interdependent relationship of both mental and physical attributes, that is to say the psycho-physical components which constitute a person.  In other words our sense of self can, upon examination, be seen as a complex flow of mental and physical events, clustered in clearly identifiable patterns, including our physical features, instincts, emotions, and attitudes, etc., continuing through time.  Further, according to Prasangika-Madhyamaka philosophy, which has become the prevailing philosophical view of Tibetan Buddhism today, this sense of self is simply a mental construct, a mere label given to this cluster of dependently arising mental and physical events in dependence on their continuity.
Now, when we look at this interdependence of mental and physical constituents from the perspective of Highest Yoga Tantram there are two concepts of a person.  One is the temporary person or self, that is as we exist at the moment, and this is labelled on the basis of our coarse or gross physical body and conditioned mind, and, at the same time, there is a subtle person or self which is designated in dependence on the subtle body and subtle mind.  This subtle body and subtle mind are seen as a single entity that has two facets.  The aspect which has the quality of awareness, which can reflect and has the power of cognition, is the subtle mind.  Simultaneously, there is its energy, the force that activates the mind towards its object- this is the subtle body or subtle mind.  These two inextricably conjoined qualities are regarded, in Highest Tantra Yoga, as the ultimate nature of a person and are identified as buddha nature, the essential or actual nature of mind.
Now, before we look more closely at the nature of the subtle body and mind, let us look at how the gross body and mind are thought to originate.  The notion of dependent origination lies at the very heart of Buddhist philosophy.  The principle of dependent origination asserts that nothing exists in its own right independent of other factors.  Things and events come into being only in dependence on the aggregation of multiple causes and conditions.  The process through which the external world and the sentient beings within it revolve in a cycle of existence propelled by karmic propensities and their interaction with misapprehension, attraction and aversion and conditions is described in terms of twelve interdependent links.  Each cycle of the process begins with a misapprehension of the nature of actual reality.  This fundamental ignorance acts as a condition for the arising of the propensities created by our past actions, mental, verbal and physical, which condition our dualising consciousness.  Our dualising consciousness, in turn, conditions the qualities and the mode of interaction of our psycho-physical aggregates, which condition our sensory fields, which generate contact, which generates sensations, and then in turn attachment, grasping, and maturation towards rebirth.  At this point there is an interaction with the genetic constituents of the parents and subsequent interaction with the environment, and then finally we have birth, ageing and death.  This cycle can be viewed as both illustration the underlying processes of life, death and rebirth and as an illustration of the processes to be transformed on the path to liberation from suffering in cyclic existence.
The notion that ther eis a connection between this life and the events of both our previous existence and our future existence, follows from the Buddhist understanding of the natural law of cause and effect.  For example, although we can speak of yesterday's weather and today's weather as distinct, today's weather is inextricably linked with the weather patterns of yesterday. Even at the bodily level, in the case of our physical health for example, we know that events in the past affect the present and those of the present the future.  Similarly, in the realm of consciousness the Buddhist view is that there is also this same causal continuum between the events of the past, present, and future.
The Buddhist understanding of the continuity of personal experience, including our memories, can also be considered here.  The Buddhist view is that the continuity of personal experience is primarily founded on the capacity for retention, which can be further developed during one's meditative practice in this life.  However, generally speaking, it is thought that if a person dies after a prolonged period of illness that has led to a prolonged degeneration of both physical and mental capacities, there will be a greater chance of many of the personal characteristics, including memories etc, being lost.  On the other hand in the case of someone who dies a sudden death, when the mind-body relationship at the gross level is still very firm, it is thought that there is a greater chance of carrying forward the acquired characteristics and memories, etc.  Nonetheless, in both cases, the characteristics carried forward from a previous life are thought to be most strongly felt at an early stage of one's rebirth.  This is because the personal characteristics of the previous life are thought, generally speaking, to be quickly overwhelmed by the developing characteristics inherited from the parents of the present life.  Nonetheless, as I have mentioned, much depends in this respect on the individual's capacity for recall and this capacity for recall is dependent on a deepened retentive training acquired in this lifetime.