Patthana Pali, the seventh and last book of the Abhidhamma, is called the Maha Pakarana, 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 Dhammasangani gives an enumeration of these dhammas classifying them under the Tika and Duka groups. Vibhanga analyses them to show what dhammas are contained in the major categories of khandhas, ayatanas, dhatus etc. Dhatukatha studies the relationship of dhammas listed in the Matika with each component of these major categories of khandhas, ayatanas and dhatus. Yamaka resolves ambiguity in the internal and external relationship of each dhamma. Patthana forming the last book of the Abhidhamma brings together all such relationship 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 earns for this treatise the reputation of being deep, profound and unfathomable.
The Buddha's teaching on the conditions for the phenomena of our life has been laid down in the last of the seven books of the Abhidhamma, the "Patthana", or "Causal Conditions and Relations". The Buddha, during the night of his enlightenment, penetrated all the different conditions for the phenomena, and he contemplated the "Dependant Origination" (Paticca Samuppada), the conditions for being in the cycle of birth and death, and the way leading to the elimination of these causes. It is said that the Buddha, during the fourth week after his enlightenment, sat in the "Jewel House", in the north west direction, and contemplated the Abhidhamma. The Abhidhamma was laid down later on in seven books. We read:
... And while he contemplated the contents of the "Dhammasangani" (the first book) , his body did not emit rays; and similarly with the contemplation of the next five books. But when, coming to the "Great Book" (the seventh book) , he began to contemplate the twenty-four universal causal relations of condition, of presentation, and so on, his omniscience certainly found its opportunity therein. For as the great fish "Timirati-pingala" (a giant fish) finds room only in the great ocean, so his omniscience truly finds room only in the Great Book. Rays of six colours- indigo, golden, red, white, tawny, and dazzling- emitted from the Teacher's body, as he was contemplating the subtle and abstruse Dhamma by his omniscience which had found such opportunity....
The teaching of the conditional relations is deep and it is not easy to understand the "Patthana", but we could at least begin to study different conditions and verify them in daily life. Before we knew the Buddha's teachings, we used to think of cause and effect in a speculative way. We may have reflected on the origin of life, on the origin of the world, we may have thought about causes and effects with regard to the events of life, but we did not penetrate the real conditions for the phenomena of life. The Buddha taught the way to develop understanding of what is true in the absolute or ultimate sense. We cannot understand the "Patthana" if we do not know the difference between what is real in conventional sense and what is real in the ultimate sense. Body and mind are real in conventional sense, they are not real in the ultimate sense. What we call body and mind are temporary combinations of different realities which arise because of conditioning factors and then fall away immediately.
They are succeeded by new realities which fall away again, and thus the flux of life goes on. Body, mind, person or being do not exist in the ultimate sense. Mental phenomena, nama, and physical phenomena, rupa, which constitute what we call a "person" are real in the ultimate sense, but they are merely passing phenomena. Ultimate truth is not abstract. Ultimate realities, in Pali: paramattha dhammas, have each their own characteristic which cannot be changed. We may change the name, but the characteristic remains the same. Seeing is an ultimate reality, it experiences visible object which appears through the eyes; it is real for everyone, it has its own unalterable characteristic. Anger has its own characteristic, it is real for everyone, no matter how we name it. Ultimate realities can be directly experienced when they appear through eyes, ears, nose, tongue, bodysense or mind. They arise because of their appropriate conditions.