Enlightenment refers to liberation from suffering and the mental toxins or “defilements” that are its cause. It is the realization of the true nature of “the way things are”. An enlightened being understands the conditioned nature of impermanent phenomena and experiences Nibbāna*, the unconditioned reality that lies behind it. The Buddha referred to this state as the “supreme happiness”. The enlightened mind is characterized by wisdom, compassion and purity. The Buddha taught that all human beings, male and female, are born with the potential for enlightenment.
The Buddha spoke of four stages of enlightenment, and thus four kinds of enlightened beings. The first of these beings is “the stream enterer”, the second is “the once returner”, the third is the “non-returner” and the final one is the fully enlightened “arahant”. Attainment of these stages is dependent on practice of the Buddha’s Eightfold Path. Their achievement is signalled by the complete and utter disappearance of certain toxic mental states from the mind. No regress is possible from such a state. One who reaches the first stage of enlightenment may be sure of reaching the final stage within seven lifetimes at most. He or she has entered the stream leading irrevocably to the ocean of Nibbāna.
*Pali: Nibbāna; Sanskrit: Nirvāna.