After Buddha Shakyamuni’s death, his teachings were first orally transmitted. His first disciples refused to put his sermons down on paper as they were convinced that important truths were to be transmitted orally, from the master to his disciple and it was up to the master to decide if the disciple was ready to reach the following stage. They gradually realized that it was necessary to classify these teachings in an order which would enable people to memorize them so that they could be transmitted to future generations. They did not classify them in a chronological order but in groups of equal length or identical content, in the form of a book called a sutra. In Sanskrit the word sutra originally means a thread similar to the one used to join the pearls of a necklace. It is said that there exists a great number of sutras, more than 84000!
“This is what I have heard”
Almost all the sutras start with the expression: «this is what I have heard”, in which the “I” traditionally refers to Ananda, Buddha’s disciple, the main witness and listener to his teachings, who accompanied him till the end. But we now know that all the sutras do not date back to the period of time when Shakyamuni lived. So, beside their number there is also a problem with their chronology. When closely looking at all the corpus of the sutras, we can perceive that some texts were prior to others and even the oldest sutras contain ancient texts mixed with more recent ones. Likewise adopted points of view and the description of some scenes largely diverge according to the sutras. This is the result of the fact that, during the 45 years of his predication, Buddha delivered a great number of speeches. Indeed his method consisted in adapting his teachings to the listeners’ capacities. This is the reason why his speeches’ transcribers tried to carefully note down the specific circumstances of their transmission within each sutra.
Indeed there was a period when the classics of Theravada Buddhism, also called The Ancients’ Doctrine which had been transmitted in South-East Asia, were considered as very ancient and directly linked to Shakyamuni himself but we now know that a great number of passages had been added very late until these sutras adopted their present form. However, assuredly, some of these sutras are contemporary to Buddha’s and his direct disciples’ life.
So Buddha taught according to people’s capacities and circumstances as the innumerable sutras testify it. Some sutras develop specific aspects of Buddha’s teaching; others are dedicated to the introduction of great figures belonging to the Buddhist pantheon. The great major sutras have become the reference texts of great Buddhist traditions and movements, throughout Eastern countries, and also presently Western countries, following the paths where they had been spread across the centuries.