Although this third book of Abhidhamma Pi¥aka is a small treatise, it ranks with the first two books forming an important trilogy, which must be thoroughly digested for the complete understanding of the Abhidhamma. Vibha³ga, the second book, has one complete chapter devoted to the analysis of dhætus, but the subject matter of dhætu is so important that this separate treatise is devoted to it for a thorough consideration. The method of analysis here is different from that employed in the Vibha³ga.
Dhætukathæ studies how the dhammas listed in the Tikas and Dukas of the Mætikæ are related to the three categories of khandha, æyatana and dhætu in their complete distribution i.e., five khandhas, twelve æyatanas and eighteen dhætus. These are discussed in fourteen ways of analytical investigations which constitute the fourteen chapters of Dhætukathæ.