The Dhammasaṅgiṇī, the first book of the Abhidhamma, and the Paṭṭhāna, the last book, are the most important of the seven treatises of Abhidhamma, providing as they do the quintessence of the entire Abhidhamma.

The Dhammasaṅgaṇī enumerates all the dhammas (phenomena) i.e., all categories of nāma, namely, consciousness and mental concomitants; and rūpa, (corporeality). Having enumerated the phenomena, they are arranged into various categories to bring out their exact nature, function and mutual relationship both internally (in our own being) and with the outside world.

The second book of the Abhidhamma Piṭaka, Vibhaṅga, together with the first book of the Dhammasaṅgaṇī and the third book of the Dhātukathā, forms a closely related foundation for the proper and deep understanding of the Buddha’s Dhamma. Whereas Dhammasaṅgaṇī provides a bird’s eye view of the whole Tika and Duka groups with further systematic arrangements under classified heads, Vibhaṅga and Dhātukathā give a closer view of selected portions of those groups bringing out minute details.

Thus, Kotthāsa Vāra in Dhammasaṅgaṇī explains the way in which khandha, āyatana, dhātu, āhāra, indriya, jhānaṅga, and so on, are included in the Tika and Duka groups. However it does not furnish complete information about these dhammas. It is Vibhaṅga which provides full knowledge concerning them, stating the exact nature of each dhamma, its constituents and its relationship to other dhammas.

The Vibhaṅga is divided into eighteen chapters each dealing with a particular aspect of the Dhamma, its full analysis and investigation into each constituent. The arrangement and classification into groups and categories follows the same system as in Dhammasaṅgaṇī. Vibhaṅga may therefore be regarded as complementary to the Dhammasaṅgaṇī.

A small treatise written in the form of a catechism, discussing all phenomena of existence with reference to the three categories, khandha, āyatana and dhatu.

Although this third book of Abhidhamma Piṭaka is a small treatise, it ranks with the first two books forming an important trilogy, which must be completely digested for the complete understanding of the Abhidhamma. Vibhaṅga, the second book, has one complete chapter devoted to the analysis of dhātus, but the subject matter of dhātu is so important that this treatise is devoted to it for a thorough consideration. The method of analysis here is different from that employed in the Vibhaṅga.

Dhātukathā studies how the Dhamma listed in the Tikas and Dukas of the Mātikās are related to the three categories of khandha, āyatana and dhātu in their complete distribution i.e., five khandhas, twelve āyatanas and eighteen dhātus. These are discussed in fourteen forms of analytical investigation which constitute the fourteen chapters of Dhātukathā.

A small treatise giving a description of various types of individuals according to their stage of achievement along the path.

Abhidhamma is mainly concerned with the study of abstract truths in absolute terms. But in describing the dhammas in their various aspects, it is not possible to keep to absolute terms only. Inevitably, conventional terms of every day language have to be employed in order to keep the lines of communication open at all. Abhidhamma states that there are two main types of conventional usage; the first type is concerned with terms which describe things that actually exist in reality and the second type describes things which have no existence in reality.

The first three books of the Abhidhamma investigate the absolute truth of the Dhamma in a planned system of detailed analysis employing such terms as khandha, āyatana, dhātu, sacca and indriya. These terms are mere designations which express things that exist in reality and can therefore be classified as conventional usage of the first type referred to above. To the second category of conventional usage belong such expressions such as man, woman, deva, individual etc., which have no existence in reality, but nevertheless are essential for the communication of thoughts.

It becomes necessary therefore to distinguish between these two types of apparent truths. But as the terms khandha, āyatana, dhātu, sacca and indriya have been elaborately dealt with in the first three books, they are dealt with here only briefly. Terms of the second type relating to individuals are given more weight and space in this treatise, hence its title Puggalapaññatti (designation of individuals). Different types of individuals are classified, in ten chapters of the book, according to the manner of enumeration employed in the Aṅguttara Nikāya.

A compilation by the Venerable Moggaliputta, the presiding thera of the Third Great Synod in which he discusses and refutes doctrines of other schools in order to uproot all points of controversy on the Buddha Dhamma.

Kathāvatthu, like Puggalapaññatti, falls outside the regular system of the Abhidhamma. It does not directly deal with the complex nature of the Dhamma. It is mainly concerned with wrong views such as “person exists; self exists; jīva exists” which were prevalent even in the Buddha’s time; or wrong views such as “arahat falls away from arahatship” which arose after the parinibbāna of the Buddha.

About two hundred and eighteen years after the parinibbāna of the Buddha there were altogether eighteen sects, all claiming to be followers of the Buddha’s teaching. Of these only the Theravādins were truly orthodox, while the rest were all schismatic. The emperor Asoka set about removing the impure elements from the order with the guidance and assistance of the elder Moggaliputtatissa who was an accomplished arahat. Under his direction, the order held in concord the uposatha ceremony which had not been held for seven years because of dissensions and the presence of false bhikkhus in the order.

At that assembly, the Venerable Moggaliputtatissa expounded on points of views, made up of five hundred orthodox statements and five hundred statements of other views, in order to refute the wrong views that had crept into the Sangha and that might in the future arise. He followed the heads of discourses, Mātikā, outlined by the Buddha himself and analysed them in detail into one thousand statements of views. This collection of statements of views was recited by one thousand selected theras who formed the Third Great Synod, to be incorporated into the Abhidhamma Piṭaka.

The style of compilation of this treatise is quite different from that of other treatises, written as it is in the form of dialogue between two imaginary debaters, one holding the heterodox views of different sects and the other representing the orthodox views.

Yamaka is regarded as a treatise on applied logic in which analytical procedure is arranged in pairs.

The Dhammasaṅgaṇī, the Vibhaṅga and the Dhātukathā examine the world of reality, named saṅkhāraloka. Puggalapaññatti and Kathāvatthu deal with beings and individuals which also exist in their own world of apparent reality, known as sattaloka. Where the dhamma of saṅkhāraloka and beings of the sattaloka co-exist is termed okāsaloka. Yamaka sets out to define and analyse the interrelationship of dhammas and puggalas as they exist in these three worlds.

This is accomplished in the form of pairs of questions, which gives it the title of Yamaka. The logical processes of conversion (anuloma) and complete inversion (paṭiloma) are applied to determine the full implications and limitations of a term in its relationship with the others. Any equivocal elements of a term (saṃsaya) are avoided by showing, through such arrangement of questions, how other meanings of the term do not fit in a particular context.

The following pairs of questions may be taken as an example:

To the question, “May all rūpa be called rūpakkhandha?” the answer is “Rūpa is also used in such expressions as piya rūpa (loveable nature), eva rūpa (of such nature), but there it does not mean rūpakkhandha.“

But to the question “May all rūpakkhanda be called rūpa?” the answer is “Yes”, because rūpakkhandha is a very wide term and includes such terms as piya rūpa, eva rūpa, etc.

Paṭṭhāna is a gigantic treatise which together with Dhammasaṅgaṇī, the first book, constitutes the quintessence of the Abhidhamma Piṭaka. It is a minutely detailed study of the doctrine of conditionality, based on twenty-four paccayas, conditions or relations.

Paṭṭhāna Pāḷi, the seventh and last book of the Abhidhamma, is called the Mahā Pakāraṇa, the “Great Book” announcing the supreme position it occupies and the height of excellence it has reached in its investigations into the ultimate nature of all the dhammas in the universe.

The Dhammasaṅgaṇī gives an enumeration of these dhammas classifying them under the Tika and Duka groups. Vibhaṅga analyses them to show what dhammas are contained in the major categories of khandhas, āyatanas, dhātus etc. Dhātukathā studies the relationship of dhammas listed in the Mātikā with each component of these major categories of khandhas, āyatanas and dhātus. Yamaka resolves ambiguity in the internal and external relationship of each dhamma. Paṭṭhāna forming the last book of the Abhidhamma brings together all such relationships in a co-ordinated form to show that the dhammas do not exist as isolated entities but they constitute a well ordered system in which the smallest unit conditions the rest of it and is also being conditioned in return. The arrangement of the system is so very intricate, complex, highly thorough and complete that it has earned for this treatise the reputation of being deep, profound and unfathomable.