The Historicity of Mahayana Scriptures
Like other Buddhist scriptures, Mahayana sutras typically begin with the phrase “Thus have I heard,” suggesting an oral tradition going back to the Buddha himself.
Since the Buddha taught different things to different audiences, it wouldn’t be surprising if both the Mahayana and Theravada scriptures were taught by the Buddha.
Ancient India was an oral culture, and important religious texts like the Rigveda were faithfully passed down for hundreds of years before taking a written form.
I am not saying, however, that the Mahayana sutras are meant to be historical word-for-word. Both the Theravada and Mahayana sutras have literary embellishments.
As far as I know, the oldest Buddhist manuscripts, such as the Gilgit and the Gandharan manuscripts, are of Mahayana sutras.
I recently read the modern Zen master Hsuan Hua’s commentary on the Amitabha Sutra, and he takes seriously the words “Thus have I heard” in the sutra.
Why be Mahayana rather than Theravada if one doesn’t actually believe that the Buddha taught the Bodhisattva vehicle? It sort of defeats the point, in my opinion.