First Part: the Compendium of Characteristics

Chapter 1: the Three dharmas

The Bouddha said: “Matter is like foam, sensation like a bubble, perception like a mirage, formations like a banana tree, and consciousness like an illusion.” 
Asanga, in Abhidharmasamuccaya

 




The first chapter is divided in two sections
The first section details the enumeration, characteristics and definitions of the “Three dharmas”.

1- The 5 aggregates (skt: skandha ; tib: phung po) (form, sensation, perception, formations, and consciousness) represent the ways in which the self appears, namely, the self as the physical body; as the basic sensations of pain and pleasure; as identification with perception; as the constructor of all karmic formations, and as the consciousness in term of basis for all these.

2 - The 18 elements (skt: dhatu; tib: khams): On the basis of the six sense faculties that apprehend their six objects, the experience of a self maintains itself in the present and the past through mental formations and the various consciousnesses. The elements are the base out of which all phenomena arise. Therefore, the elements are the seed of the functioning of cause and effect (karma).
For example: "What characterizes the element of the visual consciousness? It is a reaction to a visible form, which has the eye as its subject and the form as its object, and as a result a seed accumulated in the fundamental mindstream (alaya)".
Asanga: Abhidharmasamuccaya

3 - The 12 spheres (skt: ayatana ; tib: skye mched bcu gnyis) are the twelve sources of cognition: the inner six organs that apprehend (eye, ear, nose, tongue, skin, mind) and the outer six objets which are apprehended (form, sound, odour, taste, touch, mental object). They include all conditioned and unconditioned phenomena.
The sense objects, the sense organs, and the associated consciousnesses are the source, or the access door to future experience.

"They are the necessary medium for giving birth to and developing dualistic knowledge in terms of subject and object".
Cornu Phillippe, in Dictionnaire encyclopédique du bouddhisme

The Bouddha said: “Matter is like foam, sensation like a bubble, perception like a mirage, formations like a banana tree, and consciousness like an illusion".

"The meaning of these words is the absence of self, of impurity, of a lack of satisfaction, an absence of solidity and of substantialness". 
Asanga, in The Anthology of Special Topics of Knowledge, translated and commented by Walpola Rahula

The second section is "The division of aspects"

Following this common structure of the Abhidharma, Asanga adds a second section, “the division of aspects (or associations)”, which again takes up the three dharmas, discussing them under several different aspects, such as their substance, their designation, their relative and ultimate aspects.

This section seeks to establish the absence of self (skt: atman; tib: bdag) of all phenomena. 

Through analyses according to the division of aspects, the student understands the defective nature of mental obscurations associated with the notion of a self. By meditating on the aggregates, the elements and the ayatanas as well as the erroneous behaviour it ensues, the student can abandon the very cause of suffering.

What is the absence of illusion? It is the knowledge of the result of actions... Its function is to provide a foundation to the stopping of bad actions.

Asanga: in The Anthology of Special Topics of Knowledge,
translated and commented by Walpola Rahula 

Chapters 2, 3, and 4

The second, third and fourth chapters give a synthetic view over the "three dharmas", which represent the entire range of phenomena. They are structured and analysed in such a way that the student understands the interaction of aggregates, elements and spheres (skandha, dhatu and ayatana) and integrates the reality of phenomena as being "mind-only" (skt: cittamatra; tib: sems tsam). It shows the falsity of belief in a self which experiences, perceives, desires, and remembers.
Moreover, the student is led to understand what to cultivate and what to give up to attain perfect buddhahood.