Disclaimer: this post is based on the Theravada school of Buddhism, and specifically the Pali Canon. It is also based on modern English translations of >2000 year old teachings. In other words, ‘This is what I heard.’
Reincarnation is an important concept in Buddhism. Buddha describes the attainment of knowledge of his past lives as key to achieving Enlightenment. He also frequently pronounces the nature of the next life of a recently deceased follower. Buddha espoused the doctrine of “no-self,” stating that concepts like “I,” “me,” and “mine” should be abandoned. A person is merely a collection of aggregates, none of which persist after death. He specifically denied any continuation of consciousness from one life to the next. If there is no self, and no continuation of consciousness, in what sense can a person be said to have a previous, or next, life?
Buddha describes the night of his Enlightenment, and the seven days of meditation leading up to it, as a guide for his followers to replicate his results. He first gained knowledge of his own previous lives (“Thus with their aspects and particulars I recollected my many past lives”) before understanding the arising and passing away of all beings, and how their actions in one life created the conditions for the next (“I understood how beings pass on according to their actions”). These realizations directly preceded his conceptualization of the Four Noble Truths, the foundations of Buddhist philosophy, and his final liberation from suffering (MN 4).
Much earlier on the path to Enlightenment is the abandoning of “identity view.” Identity view is described as associating any phenomena with a “self”. Buddhism views a person as being made of five aggregates: physical form, feelings, perceptions, thoughts, and consciousness. To overcome identity view, a follower should consider how a self cannot be found in any of the aggregates, individually or in combination. “All material form should be seen with proper wisdom thus: ‘This is not mine, this I am not, this is not my self’” (MN 22), and so on for the other aggregates. This ultimately leads to the proclamation “sabbe dhamma anatta,” “all dharmas are not-self” (MN 35). The word “dharma” has many meanings in different contexts, but here it refers to phenomena, or more simply, “things.” There is nothing that can be identified as a self. As the nun Vajirā explains “Why now do you assume ‘a being’? Is that your speculative view? This is a heap of sheer formations: here no being is found” (SN 5).
Consciousness is merely one of the five aggregates, the awareness and function of the mind. It is not above cause and effect, and therefore not permanent. In one Sutra, a monk makes the mistake of thinking that consciousness continues from one life to the next, saying “as I understand the Dharma, it is this same consciousness that runs and wanders through the round of rebirths, not another.” Buddha corrects him by explaining that consciousness originates dependent on the physical body, and does not exist independently. As with all five aggregates, it arises and ceases as part of the process of the cycle of birth and death (MN 38).
So what links one life to the next, if no aspect of a person continues? Only karma endures. Karma is the action that causes an effect (or “bears fruit,” as described in the Sutras). Actions taken in one life may have effects in others; the chain of causation is unbroken by the arising and passing away of beings. In Buddhism, the karma generated in a person’s life determines the circumstances of their rebirth in the next. Karma is a debt that must be paid.
Why would Buddha say “I recollected my many past lives,” if he teaches that there is nothing that can be considered “mine,” and nothing that can be pointed to as “I”? Buddha describes engaging in linguistic conventions in order to make the teaching comprehensible. When talking about his use of pronouns and describing the various kinds of self, he says “these are mere names, expressions, turns of speech, designations in common use in the world, which the Tathāgata uses without misapprehending them” (DN 9). “Tathāgata” itself is a convention, a title Buddha uses to avoid referring to himself (kind of an early take on TAFKAP: The Aggregates Formerly Known As Gautama). Buddha might have said “this collection of aggregates gained knowledge of the previously existing collections of aggregates which took actions that created the conditions for this collection of aggregates to exist and arrive at this point.” But “I recollected my many past lives” is not only more comprehensible, it was also in keeping with the common beliefs of his followers.
The teaching of karma is tied into morality, to solve the problem of good or bad actions not necessarily yielding a corresponding result. Most religions suggest actions will have consequences after death, via some reward or punishment, and karma is no different. This holds true even when karma is disassociated with continuation of consciousness. The good or bad effects of karma must occur sometime, to someone. But identifying with such things will leave one in the weeds, as Buddha describes when he is questioned by the wanderer Vacchagotta. The wanderer asks if Master Gautama holds various views, such as “the world is eternal,” or “the world is not eternal,” or “the soul and the body are the same, or two different things,” or “does an enlightened being exist after death.” Buddha replies that he does not hold any “speculative views” because “with the cessation of all conceivings, all I-making, all mine-making, the Tathāgata is liberated.” When asked where he will reappear after death, Buddha says “the term ‘reappear’ does not apply,” like asking of an extinguished fire what direction it went (MN 72).
Notes:
Citations refer to the volumes of the Pali Cannon:
DN = Digha Nikaya, The Long Discourses
MN = Majjhima Nikaya, The Medium Length Discourses
SN = Samyutta Nikaya, The Connected Discourses
The number refers to the number of a Sutra within that volume.