Buddhaghosa hung the entire work on a single canonical verse, in which one established in virtue develops concentration and understanding, and the three trainings give the book its architecture. The opening chapters treat sila, virtue: the monk's restraint, the four kinds of purity, and the ascetic practices that support them.
The long middle section treats samadhi, concentration. Here Buddhaghosa catalogues the forty meditation subjects, the kammatthana, from the ten coloured and elemental discs called kasinas through the recollections of the Buddha, the divine abidings of loving-kindness, compassion, gladness and equanimity, to the repulsiveness contemplations and the analysis of the body, and he specifies for each the temperament it suits, greedy, hating, deluded, faithful, intelligent or speculative, the procedure for developing it, and the level of absorption it can reach. The section on the jhanas, the absorptions, with their factors and masteries, and on the supernormal knowledges that concentration makes possible, became the tradition's standard account. The final section treats panna, understanding: the aggregates, sense bases, faculties and dependent origination as the soil of insight, then the progressive purifications and the insight knowledges, rising through the contemplations of impermanence, suffering and non-self to path, fruit and the assurance of liberation. The whole is studded with similes and stories from the commentarial tradition, teaching by image as much as by list.