Theravada  Buddhism (literally, "the Teaching of the Elders", or "the Ancient Teaching") is the oldest and most traditional of the Buddhist Schools.

It is closely based on the Pali Cannon, the oldest texts of Buddhism, transcribed during the 4th Buddhist Council, about 1st Century BC.

It is predominant religion of Sri Lanka (about 70% of the population) and most of continental Southeast Asia (Cambodia, Laos, Burma, Thailand).


From Wikipedia:

Theravada promotes the concept of Vibhajjavada (Pali), literally "Teaching of Analysis." This doctrine says that insight must come from the aspirant's experience, critical investigation, and reasoning instead of by blind faith; however, the scriptures of the Theravadin tradition also emphasize heeding the advice of the wise, considering such advice and evaluation of one's own experiences to be the two tests by which practices should be judged.

In Theravada, the cause of human existence and suffering (dukkha) is identified as craving (tanha), which carries with it the defilements (which are anger, ill will, aversion, greed, jealousy, conceit, hatred, fear, sensual desire, obsession, passion, irritation, distraction, vengeance, depression, anxiety, clinging to the body, etc.). The level of defilement can be coarse, medium, and subtle. It is a phenomenon that frequently arises, remains temporarily and then vanishes. Theravadins believe defilements are not only harmful to oneself, but also harmful to others. They are the driving force behind all inhumanities a human being can commit.

Theravadins believe these defilements are the habits born of ignorance (avijja) which afflict the minds of all unenlightened beings. It is believed that unenlightened beings are under the influence of the defilements, unenlightened beings cling to them through ignorance of the truth. But in reality, those mental defilements are nothing more than taints that have afflicted the mind and create suffering and stress. It is also believed that unenlightened beings cling to the body, assuming it as their own "Self", but in reality the body is an impermanent phenomenon formed from the 4 basic elements (often characterized by Earth, Water, Fire and Air) and after death the body will decompose and disperse. The mental defilements' frequent instigation and manipulation of the mind is believed to have prevented the mind from seeing the true nature of reality. Unskillful behavior in turn can strengthen the defilements, but following the Noble Eightfold Path can weaken or eradicate them.