Reincarnation isn't exactly a doctrine, but a supposition. The dharma (practice or work) of Buddhism is to reach a state of perfect understanding, and until that is reached the person will be reborn to continue the work. However, not all who believe Buddhist ideals of right living and nonviolence and call themselves Buddhists believe in reincarnation. Bottom line answer: mostly Buddhists do believe in reincarnation; it's implied by the Buddha's teaching; but they don't have to. Answer: Buddhists are pretty much a do it for yourself organization. The Buddha said ""Do not accept what you hear by report, do not accept tradition, do not accept a statement because it is found in our books, nor because it is in accord with your belief, nor because it is the saying of your teacher....Be ye lamps unto yourselves."