REASONS TO BELIEVE IN REBIRTH
"I recalled my varied lot in former existences."
-- MAJJHIMA NIKĀYA
How are we to believe in rebirth?
The Buddha is our greatest authority on rebirth. On the very night of His Enlightenment, during the first watch, the Buddha developed retro-cognitive knowledge which enabled Him to read His past lives.
"I recalled," He declares, "my varied lot in former existences as follows: first one life, then two lives, then three, four, five, ten, twenty, up to fifty lives, then a hundred, a thousand, a hundred thousand and so forth. "
During the second watch the Buddha, with clairvoyant vision, perceived beings disappearing from one state of existence and reappearing in another. He beheld the "base and the noble, the beautiful and the ugly, the happy and the miserable, passing according to their deeds."
These are the very first utterances of the Buddha regarding the question of rebirth. The textual references conclusively prove that the Buddha did not borrow this stern truth of rebirth from any pre-existing source, but spoke from personal knowledge -- a knowledge which was supernormal, developed by Himself, and which could be developed by others as well.
In His first paean of joy (udāna), the Buddha says:
"Through many a birth (anekajāti), wandered I, seeking the builder of this house. Sorrowful indeed is birth again and again (dukkhājātipunappunam). "
In the Dhammacakka Sutta,  His very first discourse, the Buddha, commenting on the second Noble truth, states: "This very craving is that which leads to rebirth" (y'āyam tanhā ponobhavikā). The Buddha concludes this discourse with the words: "This is my last birth. Now there is no more rebirth (ayam antimā jāti natthi dāni punabbhavo)."
The Majjhima Nikāya relates that when the Buddha, out of compassion for beings, surveyed the world with His Buddha-vision before He decided to teach the Dhamma, He perceived beings who, with fear, view evil and a world beyond (paralokavajjabhayadassāvino). 
In several discourses the Buddha clearly states that beings, having done evil, are, after death (parammaranā), born in woeful states, and beings having done good, are born in blissful states. Besides the very interesting Jātaka stories, which deal with His previous lives and which are of ethical importance, the Majjhima Nikāya and the Anguttara Nikāya make incidental references to some of the past lives of the Buddha.
In the Ghatikāra Sutta,  the Buddha relates to the Venerable Ānanda that He was born as Jotipāla, in the time of the Buddha Kassapa, His immediate predecessor. The Anāthapindikavāda Sutta  describes a nocturnal visit of Anāthapindika to the Buddha, immediately after his rebirth as a Deva. In the Anguttara Nikāya,  the Buddha alludes to a past birth as Pacetana the wheelright. In the Samyuttta Nikāya, the Buddha cites the names of some Buddhas who preceded Him.
An unusual direct reference to departed ones appears in the Parinibbāna Sutta.  The Venerable Ānanda desired to know from the Buddha the future state of several persons who had died in a particular village. The Buddha patiently described their destinies.
Such instances could easily be multiplied from the Tipitaka to show that the Buddha did expound the doctrine of rebirth as a verifiable truth. 
Following the Buddha's instructions, His disciples also developed this retro-cognitive knowledge and were able to read a limited, though vast, number of their past lives. The Buddha's power in this direction was limitless.
Certain Indian Rishis, too, prior to the advent of the Buddha, were distinguished for such supernormal powers as clairaudience, clairvoyance telepathy, telesthesia, and so forth.
Although science takes no cognizance of these supernormal faculties, yet, according to Buddhism, men with highly developed mental concentration cultivate these psychic powers and read their past just as one would recall a past incident of one's present life. With their aid, independent of the five senses, direct communication of thought and direct perception of other worlds are made possible.
Some extraordinary persons, especially in their childhood, spontaneously develop, according to the laws of association, the memory of their past births and remember fragments of their previous lives. (Pythagoras) is said to have distinctly remembered a shield in a Grecian temple as having been carried by him in a previous incarnation at the siege of
Experiences of some dependable modern psychists, ghostly phenomena, spirit communication, strange alternate and multiple personalities  also shed some light upon this problem of rebirth.
In hypnotic states some can relate experiences of their past lives, while a few others, like Edgar Cayce of
The phenomenon of secondary personalities has to be explained either as remnants of past personal experiences or as "possession by an invisible spirit." The former explanation appears more reasonable, but the latter cannot totally be rejected.
How often do we meet persons whom we have never before met, but who, we instinctively feel, are familiar to us? How often do we visit places and instinctively feel impressed that we are perfectly acquainted with those surroundings? 
The Dhammapada commentary relates the story of a husband and wife who, seeing the Buddha, fell at His feet and saluted Him, saying -- "Dear son, is it not the duty of sons to care for their mother and father when they have grown old. Why is it that for so long a time you have not shown yourself to us? This is the first time we have seen you?"
The Buddha attributed this sudden outburst of parental love to the fact that they had been His parents several times during His past lives and remarked:
"Through previous association or present advantage
That old love springs up again like the lotus in the water. "
There arise in this world highly developed personalities, and Perfect Ones like the Buddhas. Could they evolve suddenly? Could they be the products of a single existence?
How are we to account for personalities like Confucius, Pānini, Buddhaghosa, Homer and Plato, men of genius like Kāli?āsa, Shakespeare, infant prodigies like Ramanujan, Pascal, Mozart, Beethoven and so forth?
Could they be abnormal if they had not led noble lives and acquired similar experiences in the past? Is it by mere chance that they are born of those particular parents and placed under those favourable circumstances?
Infant prodigies, too, seem to be a problem for scientists. Some medical men are of opinion that prodigies are the outcome of abnormal glands, especially the pituitary, the pineal and the adrenal gland. The extra-ordinary hypertrophy of glands of particular individuals may also be due to a past Kammic cause. But how, by mere hypertrophy of glands, one Christian Heineken could talk within a few hours of his birth, repeat passages from the Bible at the age of one year, answer any question on Geography at the age of two, speak French and Latin at the age of three, and be a student of philosophy at the age of four; how John Stuart Mill could read Greek at the age of three; how Macaulay could write a world history at the age of six; how William James Sidis, wonder child of the United States, could read and write at the age of two, speak French, Russian, English, German with some Latin and Greek at the age of eight; how Charles Bennet of Manchester could speak in several languages at the age of three; are wonderful events incomprehensible to non- scientists. Nor does science explain why glands should hypertrophy in just a few and not in all. The real problem remains unsolved.
Heredity alone cannot account for prodigies, "else their ancestry would disclose it, their posterity, in even greater degree than themselves, would demonstrate it."
The theory of heredity should be supplemented by the doctrine of Kamma and rebirth for an adequate explanation of these puzzling problems.
Is it reasonable to believe that the present span of life is the only existence between two eternities of happiness and misery? The few years we spend here, at most but five score years, must certainly be an inadequate preparation for eternity.
If one believes in the present and a future, it is logical to believe in a past.
If there be reason to believe that we have existed in the past, then surely there are no reasons to disbelieve that we shall continue to exist after our present life has apparently ceased. 
It is indeed a strong argument in favour of past and future lives that "in this world virtuous persons are very often unfortunate and vicious persons prosperous. "
We are born into the state created by ourselves. If, in spite of our goodness, we are compelled to lead an unfortunate life, it is due to our past evil Kamma. If, in spite of our wickedness, we are prosperous, it is also due to our past good Kamma. The present good and bad deeds will, however, produce their due effects at the earliest possible opportunity.
A Western writer says:
"Whether we believe in a past existence or not, it forms the only reasonable hypothesis which bridges certain gaps in human knowledge concerning facts of everyday life. Our reason tells us that this idea of past birth and Kamma alone can explain, for example, the degrees of differences that exist between twins; how men like Shakespeare with a very limited experience are able to portray, with marvellous exactitude, the most diverse types of human character, scenes, and so forth, of which they could have no actual knowledge, why the work of the genius invariably transcends his experience, the existence of infant precocity, and the vast diversity in mind and morals, in brain and physique, in conditions, circumstances and environments, observable throughout the world."
What do Kamma and Rebirth explain?
1. They account for the problem of suffering for which we ourselves are responsible.
2. They explain the inequality of mankind.
3. They account for the arising of geniuses and infant prodigies.
4. They explain why identical twins who are physically alike, enjoying equal privileges, exhibit totally different characteristics, mentally, morally, temperamentally and intellectually.
5. They account for the dissimilarities amongst children of the same family, though heredity may account for the similarities.
6. They account for the extraordinary innate abilities of some men.
7. They account for the moral and intellectual differences between parents and children.
8. They explain how infants spontaneously develop such passions as greed, anger and jealousy.
9. They account for instinctive likes and dislikes at first sight.
10. They explain how in us are found "a rubbish heap of evil and a treasure-house of good."
11. They account for the unexpected outburst of passion in a highly civilised person, and for the sudden transformation of a criminal into a saint.
They explain how profligates are born to saintly parents, and saintly children to profligates.
13. They explain how, in one sense, we are the result of what we were, we will be the result of what we are; and, in another sense, we are not absolutely what we were, and we will not be absolutely what we are.
14. They explain the causes of untimely deaths and unexpected changes in fortune.
15. Above all they account for the arising of omniscient, perfect spiritual teachers, like the Buddhas, who possess incomparable physical, mental, and intellectual characteristics.