“Hearers” of the Lesser Vehicle usually sought as their goal the fulfillment of their own private training. They expected others to imitate the strict practices which they performed, and had little patience with ordinary people caught up in the problems of everyday life.
Purna was an exception. He looked like a sravaka, but he went about preaching the law to common people, and doing so with such eloquence that he was able to cause many of them to aspire to supreme-perfect-enlightenment. Therefore, in reality he was not a sravaka at all, but a Bodhisattva (one who devotes his life to helping others). Any Bodhisattva must also be a preacher (otherwise he cannot help anyone), and that is why a Bodhisattva is called a “teacher of the law.” From Chapter Ten on, the Lotus Sutra will clarify the mission of Bodhisattvas. (Here it is only suggested.)
Introduction to the Lotus Sutra