The earliest available teachings of the Buddha are to be found in Pali literature and belongs to the school of the Theravadins, who may be called the most orthodox school of Buddhism. This school admits the human characteristics of the Buddha, and is characterised by a psychological understanding of human nature; and emphasises a meditative approach to the transformation of consciousness.
The teaching of the Buddha according to this school is very plain. He asks us to ‘abstain from all kinds of evil, to accumulate all that is good and to purify our mind’. These can be accomplished by The Three Trainings: the development of ethical conduct, meditation and insight-wisdom.
The philosophy of this school is straight forward. All worldly phenomena are subject to three characteristics - they are impermanent and transient; unsatisfactory and that there is nothing in them which can be called one's own, nothing substantial, nothing permanent. All compounded things are made up of two elements - the non-material part, the material part. They are further described as consisting of nothing but five constituent groups, namely the material quality, and the four non-material qualities - sensations, perception, mental formatives and lastly consciousness.