Some Shia folks claim that not all the Hadith mentioned in Biharul Anwar by Allama Baqir Majlisi are authentic. Is this true? If so, what proportion is inauthentic?
Bismihi ta'ala
Other than the holy Quran, we do not have a book that is completely authentic, from cover to cover. Even our early hadith books like al-Kafi, etc, are to be individually evaluated and scrutinised by experts of hadith grading.
The great book Bihar al-Anwar, by al-'Allamah al-Majlisi (q.s.) is no exemption as well. As for percentage or proportion, that cannot be defined as a whole, because each scholar could have different methodology of grading authenticity, and other related issues to hadith grading.
And Allah knows best