A number of theories have been proposed regarding Avicenna's madhab (school of thought within Islamic jurisprudence). Medieval historian Ẓahīr al-dīn al-Bayhaqī (d. 1169) considered Avicenna to be a follower of the Brethren of Purity. On the other hand, Dimitri Gutas along with Aisha Khan and Jules J. Janssens demonstrated that Avicenna was a <answer>Sunni</answer> Hanafi. However, the 14th cenutry Shia faqih Nurullah Shushtari according to Seyyed Hossein Nasr, maintained that he was most likely a Twelver Shia. Conversely, Sharaf Khorasani, citing a rejection of an invitation of the <answer>Sunni</answer> Governor Sultan Mahmoud Ghazanavi by Avicenna to his court, believes that Avicenna was an Ismaili. Similar disagreements exist on the background of Avicenna's family, whereas some writers considered them <answer>Sunni</answer>, some more recent writers contested that they were Shia.
What Islamic denomination was Avicenna thought to be a member of?
Sunni