The emergence of Islamic reformist thinking in the period of the so-called Nahḍah (Renaissance), in particular in the latter part of the XIX century, entailed a revival of interest in Muʿtazilite rationalism. Among the Sunni intellectuals who reevaluated the ancient theological school, a prominent place belongs to Aḥmad Amīn (1886–1954). Muʿtazilism takes up much space in his famous trilogy Fajr al-Islām (The Dawn of Islam), Ḍuḥā al-Islām (The Morning of Islam) and Ẓuhr al-Islām (The Noon of Islam). Although the trilogy has been defined as the first critical research work carried out by a Muslim writer on Islamic civilisation, it has not been the subject of any specific or in-depth studies. The present article aims to partially fill this gap through a detailed linguistic and content analysis of selected passages from the trilogy. This analysis shows how Aḥmad Amīn’s interpretation of the Muʿtazilism fits into the wider project that he pursued to reform Islam: on the one hand, he fought against the traditional dependence on transmitted data (naql), which he considered to be the main cause of the intellectual stasis of the Muslims; on the other hand, he promoted a critical reading of the sacred texts, the Qur’ān and Sunnah, based on reason and on modern Western scientific methodology.