http://www.angelfire.com/electronic/bodhidharma/karma_truth.html
This law of Karma, or cause and effect, is so powerful that it governs everything in the universe except, according to Buddhism, the one who is Enlightened or who recognizes basic nature. Upon Enlightenment, the round of cause and effect loses its significance, just as Samsara, or the round of birth and death, ceases with Enlightenment.
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In one of the Buddhist texts it is recorded that someone asked Buddha:
Why are some women ugly but rich?
Why are some women beautiful but poor?
Why are some people poor but with good health and a long life?
Why are some rich yet ill and short-lived?
The Buddha's answers were:
One who is ugly but rich was short-tempered in past lives easily irritated and angered but was also very generous and gave offerings to the Buddha, Dharma, and Sangha and made contributions to many sentient beings.
One who is beautiful but poor was, in past lives, very kind, always smiling and soft spoken, but was stingy and reluctant to make offerings or help other people.
The person who is poor but in good health and enjoying a long life was, in his or her past lives, very stingy or reluctant to make donations, but was kind to all sentient beings, did not harm or kill others, and also saved many sentient beings lives.
The person who is rich but often ill, or who is short-lived, was, in his or her past lives, very generous in helping others but loved hunting and killing and caused sentient beings to feel worried, insecure, and frightened.
The above examples give us some idea of why people on earth, although all human beings, vary so much in appearance, character, lifespan, health, mental ability and fate. It is even more interesting to note how much the circumstances in which a person is born can influence his or her destiny. Which race, which nation, which skin color, which era all these factors make a great difference.
Would it not be more logical to think that something was going on before one birth that caused all those effects than to say that it is purely accidental or even to say that it is God's will? If a baby has no past life, then on what grounds does God judge whether to reward or to punish that baby by causing him or her to be born under different circumstances? Intent, thought and action should always be taken into consideration.