Gombrich/What the Buddha Thought, 9. Causation and Non-random Process

For which of the Buddhaís ideas was he most famous among the mass of his followers in ancient India? The theory of karma may not have been understood by later followers to be the Buddhaís distinctive contribution, because it soon came to have such a great influence on other Indian religious traditions as well. Yes, he was associated with the teaching of 'no soul' but that was a label; the precise idea was probably understood by few. If we look, however, for the idea which provided Buddhists with their popular self-definition, my question has a clear answer. Buddhist institutions in ancient India provided pilgrims and other devotees with thousands and thousands of small terracotta plaques, most of which bore the same words.