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It has been mentioned that the author of the Tattvārthabhāṣya's commentary should indeed be Siddhasena, as it is impossible for both Śīlāṅka and Abhayadeva, from a very recent period, to use the term "Gandhahastin" for different teachers. It is hard to imagine that a learned scholar like Abhayadeva would not have seen the commentary composed by Śīlāṅkasūri on the first local Ācārāṅga in Jain Agamas. Further, where Śīlāṅka himself has quoted the verses of Siddhasena Dīvākar in his commentaries, he has not used the term "Gandhahastin" at any point. Therefore, it is clear that the Gandhahastin intended by Śīlāṅka cannot be Siddhasena Dīvākar.
Based on the reasoning above, we have also found complete supporting ancient evidence for the initial conclusion we reached, which was written by a disciple of Yaśobhadra, the supplement to Haribhadra’s incomplete commentary. It is as follows:
"By the disciple of Sūriyāśobhadra, it is extracted for the sake of self-understanding. The commentary on Tattvārtha is held, well engaged with the six chapters.
Commenced by Haribhadra, the exposition of half of the six chapters. Once again, this is re-established by the revered [scholars] from the commentary of Tattvārtha.”
Thus, it is stated that the commentary on the six chapters initiated by Haribhadra is composed by the revered Siddhasena, but a new Tattvārtha commentary has been composed by Gandhahastin, while the rest has been extracted by the teacher [the rest by me] for self-understanding, and a highly profound, fully completed commentary has been produced.
Currently, two complete commentaries of Siddhasena on Tattvārthabhāṣya are available from the Śvetāmbara teachers. One is extensive and the other is brief. The creator of the extensive commentary is indeed proposed to be Siddhasena, who is a disciple of Dinnaga.