Scholars generally believe that the Abhidharma emerged after the time of the Buddha, in around the 3rd century BCE. Therefore, the seven Abhidhamma works are generally claimed by scholars not to represent the words of the Buddha himself, but those of disciples and scholars. Factors contributing to its development could have been the growth of monastic centers, the growing support for the Buddhist sangha, and outside influences from other religious groups.

The "base upon which the entire system rests" is the 'dharma theory' and this theory 'penetrated all the early schools'. For the Abhidharmikas, the ultimate components of existence, the elementary constituents of experience were called dharmas (Pali: dhammas).

The early Buddhist scriptures give various lists of the constituents of the person such as the five skandhas, the six or 18 dhatus, and the twelve sense bases. In Abhidharma literature, these lists of dharmas systematically arranged and they were seen as the ultimate entities or momentary events which make up the fabric of people's experience of reality. The idea was to create an exhaustive list of all possible phenomena that make up the world.
Abhidamma Philosophy, Bhikkhu J. Kashyap, D.L.S. Jayawardana, maha Bodhi Book Agency, Paperback, 1942/2007, 344 pages, $12.00

Chapter I

Types of Consciousness
The World of Desires
The World of Form
The World of Formless
The Supra-Mundane
Final Calculation

Chapter II

Psychic Factors
How many and what are they?
What Factors are Present in which Types of Consciousness

Chapter III

Consiousness in relation with:
Feeling
Hetu
Function
Doors
Objects
Organs

Chapter IV

Course of Congnition Through:
The five doors of senses
The Mind-door

Chapter V

Consciousness that does not come in the course of Congnition.

Chapter VI

Material Qualities.

Chapter VII

Abhidharmmic Terms

Chapter VIII

The Philosophy of Relation
Paticcasamuppada-Naya
Ptthana-Naya

Chapter IX

Objects of Meditation
Samatha (Calm)
Vipassama (insight)