Referring to both a system of thought and a genre of literature the name Abidhamma could be translated as “Pertaining to Dhammas”. As a system of thought Abhidhamma grew out of two trends in early Buddhism. The first of these was the analytical or reductionist trend. For example the Buddha taught that the individual was made up of mind (nama) and body (rupa) which he often further analysed into the five aggregates. Each of these aggregates could again be analysed, the body for example into solidity, fluidity caloricity and space. This was as far as the Buddha himself went, but the early Buddhists continued the process of analysis until they arrived at what they believed to be the most basic constituents of reality which were called Dhammas.
These dhammas were said to be absolutes, not in the sense that they were ultimate realities but in the sense that they were not capable of being further analysed. The second trend that led to the development of Abidhamma was the particular way that change was seen. The Buddha took an empirical approach to change, seeing it as taking place gradually or at different velocities; for example he spoke of the stream of consciousness (sotavinnana). The early Buddhists however came to understand change as being a discreet momentary event. Thus all dhammas were said to arise, persist for a minute period of time and then pass completely away before the next dhamma arose.This was known as the Theory of Moments (Khanavada).
Whereas the Buddha’s teachings in the suttas are generally empirical and practical, Abidhamma is speculative and theoretical. The Sutta Pitakas of the early Buddhist schools were almost identical while the Abhidammas theories often differed greatly from each other. In fact, the early schools and later the Mahayana, arose as a result of different attempts to explain the philosophical problems created by both the Theory of Dhammas and the Theory of Moments.