Summary of pages 48-54
Several Mu'tazili writings, including works by 'Abd al-Jabbar, were discovered in Yemen by a team of Egyptian scholars in 1950.
A part of the Zaydi community which included the Mu'tazili mutakallimun - migrated to Yemen at the end of the Buyid Age (mid-eleventh century). Thus, many of the texts found turned out to be Mu'tazili kalam texts. The most significant find was six of the twenty volumes of the Kitab almughni by 'Abd al-Jabbar.
These discoveries stimulated new scholarship on kalam and the Mu'tazila in particular
The Mutazilah Qadi, Abd al-Jabbar al-Hamdani al-Astabadi, was well grounded in the traditional study of the Quran and Hadiths.
'Abd al-Jabbar first studied Ash'ari kalam (Madhab Shafii), then saw the light and became a student of Mu'tazili shaykhs (Madhab Hanafi).
one biographer noted that the Qadi worried about his Shafi'i affiliation in fiqh and thus wanted to study Hanafi fiqh, the preferred madhhab among Mu'tazili mutakallimun. His mentor, Abu 'Abdallah, who was also a distinguished Hanafi jurisconsult, advised the Qadi to remain a scholar of the Shafi'i madhhab, and that both the Hanafi and Shafi'i schools
were valid.
Qadi Abd al-Jabbar had written and produced over twenty works (books).
The text of 'Abd al-Jabbar's Kitab al-usul al-khamsa was discovered by Daniel Gimaret in a collection of manuscripts at the Vatican.
Reference
[1] Martin, Richard C, Woodward, Mark R and Atmaja, Dwi S. 1997. Defenders of Reason In Islam: Mu'tazilism and Rational Theology from Medieval School to Modern Symbol. Oneworld Oxford. Preface. ISBN 978-1851681471