Atheism has never been a singificant social or intellectual threat in the Muslim world until the emergence of the 8th century Dahriyya. These thinkers were empiricists believing all knowledge could only be acquired via the empirical method. They believed the cosmos was eternal comprising four qualities, responsible for all that existed. They argued everything had always existed and did not require a creator.
According to Faraj al-Isfahani in his Kitab al-Aghani, the famous jurist Abu Hanifa debated a Dahri in the 8th century. Abu Hanifa was known to have intellectually destroyed the Dahriyya in public debates.
Many other Islamic scholars responded to the claims of the Dahriyya, including Al-Ghazali, Ibn al-Jawzi, al-Jahiz, Muhammad b. Shabib, Ibn Qutayba and Abu 'Isa al-Warraq to mention a few.
In Al-Ghazali in his book Kimiya, describes them as reductionists, lacking a holistic understanding of the universe and its purpose. He argues they are like ants on a piece of paper that cannot lift their eyes from the ink or the pen they see before them and fail to see who is writing.