समुदाय उभयहेतुकेऽपि तदप्राप्तिः ॥ १८ ॥
samudāya ubhayahetuke’pi tadaprāptiḥ || 18 ||
samudāye—The aggregate; ubhaya-hetuke—having for its cause the two; api—even; tat-aprāptiḥ—it will not take place.
18. Even if the (two kinds of) aggregates proceed from their two causes, there would result the non-formation (of the two aggregates).
This Sutra begins the refutation of the Bauddha school. There are three principal schools of Buddhism, viz . the Realists, who accept the reality of both the outside and the inside world, consisting respectively of external things and thought; the Idealists, who maintain that thought alone is real; and the Nihilists, who maintain that everything is void and unreal. But all of them agree that everything is momentary—nothing lasts beyond a moment.
The Realists among the Bauddhas recognize two aggregates, the external material world and the internal mental world—both together making up the universe. The external world is made up of the aggregation of atoms. These atoms are of four kinds —atoms of earth, which are hard; atoms of water, which are viscid; atoms of fire, which are hot; and atoms of air, which are mobile. Of the internal world, the five Skandhas (groups) are the cause. They are—Rupa Skandha, comprising the senses and their objects; the Vijnana Skandha, comprising the series of self-cognitions which give rise to the notion of ‘I’; the Vedana Skandha, comprising pleasure, pain, etc.; the Samjna Skandha, comprising the cognition of things by names, as, he is a man; and the Samskara Skandha, comprising attachment and aversion, Dharma (merit), Adharma (demerit), etc. By the aggregation of these Skandhas the internal aggregate or the mental world is produced. These are the two internal and external aggregates referred to in the Sutras. Sutras 18-27 refute the Realists’ view.
The question now arises, how are these aggregates formed? Is there an intelligent principle behind as the cause, the guide, of the aggregation, or does it take place spontaneously? If there is an intelligent principle, is it stationary or momentary? If it is stationary, the Buddhistic doctrine of momentariness is contradicted. If it is momentary, then we cannot say that it comes into existence first and then unites the atoms, for that would mean that the cause lasts for more than one moment. Again, if there is no intelligent principle as guide, how can the non-intelligent atoms and the Skandhas aggregate in a systematic way? Moreover, the activity would be eternal, and there would be no destruction or Pralaya. For all these reasons the formation of aggregates cannot be accounted for, and in their absence there cannot exist the stream of mundane existence. Consequently, the doctrine of this school of Bauddhas is untenable.