In Buddhist thought this is the continuing cycle of birth, death and rebirth. All beings are trapped in this unpleasant cycle until they reach enlightenment. Samsara is looked upon in a negative light because of all the suffering that life entails (as elucidated in the First Noble Truth). The cause of this cycle is craving as elucidated in the Second Noble Truth. Belief in samsara does not necessarily require a belief in reincarnation in it strictest, traditional sense and it should be mentioned here that many people practice Zen but do not believe in reincarnation.