pulga wrote:How have we ascertained the accuracy of Saṃghadeva's Madhyama Āgama when we haven't the original to compare it with?
By comparing it with the Pali, basically.
pulga wrote:The whole historical setting of how these texts came to be preserved is lost to us. What sort of man was Saṃghadeva? What circumstances did he find himself in? What particular texts did he have access to? What was his standard of thoroughness and accuracy?
The historical setting of Buddhism in Central Asia and India at the time is partially recorded in the travel account of the monk Faxian. The historical setting of the translation of the Madhyama Āgama is recorded in quite some detail, however. As are the character, circumstances and interests of Saṃghadeva, and the names of the other texts he translated, and his process of translation.
The sources for these are the prefaces to Saṃghadeva's translations written by his contemporaries and a collection of monks' biographies compiled 100 years after his time. And the wider Chinese social context is recorded in stacks of official and unofficial histories.
Basically, he was a specialist in the Abhidharma from Kashmir, when he first came to China he worked on a translation team with other Indian, Central Asian and Chinese monks checking or reading out the Indic original, but not translating himself as he could not yet speak Chinese. After a decade or so in China he learnt the language and discovered that the translations he had worked on as a monolingual assistant (including the Madhyama Agama) were not accurate, so he and his followers resolved to retranslate them.
The translation process usually took place in a hall in front of an audience of local dignitaries and monks. Usually a foreign monk read out the Indic version, either from memory or from a manuscript, a monk who understood both Indian and Chinese translated it orally into Chinese, then a couple of Chinese monks would each write down the translation in Chinese. After the translation had been completed in this way it would be thoroughly checked and edited.
In the case of the Madhyama Agama the preface records that it was translated from December 15th 397 to July 24th 398 in a temple on the estate of a local official in what is modern day Nanjing by the Kashmiri Gautama Samghadeva, based on a manuscript read out to him by Samgharaksa, another Kashmiri monk. The Chinese monk Daoci acted as the scribe, assisted by Libao and Tanghua. So the public translation process finished in summer 398 but the preface records that because of the outbreak of war the editing process was not completed until 401.