What is the reason for declaring Ibn Sina, Al-Farabi, and other scholars to be disbelievers, even though applied sciences are a collective obligation (fard kifaya)? Is there a contradiction in that? And how can one explain Ibn Taymiyyah's statement about Al-Khwarizmi that "the Sharia sciences are self-sufficient without him and others," despite his significant achievements in simplifying arithmetic operations and algebra?

Islam calls for knowledge and the cultivation of the earth. Secular sciences such as medicine and arithmetic are communal obligations (fard kifaya) that are indispensable for the affairs of this world to function. If some people undertake them, the sin falls away from the rest. This does not contradict the excommunication (takfir) of some scholars like Ibn Sina, as they were not excommunicated because of their secular knowledge, but for matters related to religious knowledge, such as his denial of bodily resurrection and God’s knowledge of particulars. Religious knowledge is self-sufficient without these scholars, and their statements in matters of religion may not be free from error. It is necessary to verify the authenticity of doubts that are based on fabricated texts. Praise is for a scholar in his specialization, while condemnation is for what he stated in religious matters that are considered innovation, disbelief, or transgression.