He was a non-Brahmin preacher who was held in great esteem by the people. Buddhaghosa says that Puduka was his personal name and Katyayana was his family name (gotra). He accepted seven elementary substances as permanent and eternal, either created nor caused to be created.’
The seven elements are – earth, water, fire, air, pleasure, pain and soul. They are barren (so that nothing can be created out of them), steadfast as a mountain peak, they do not move and remain firmly fixed as a pillar. If someone with a sharp sword cuts one’s head into two no one thereby deprives anyone of life, a sword has only penetrated into the interval between seven elementary substances.
This Anuvada (atom theory) has been described in Tamil sources as Sarvatavada (Eternalism).The eternal elements, earth, water etc. unite or separate automatically without any volitional activity. The two elements, pleasure and pain, stand for some factors calling forth a union of those elements just like adrsta in vaisesika system.