The aim of this article is to illustrate the two human conceptions introduced in the Basran School of Muʿtazila with their reflections on the fields like theoretical physics, epistemology, and ethics. In the Muʿtazilite school that started off with al-Naẓẓām, continued with al-Jāḥiẓ and was grounded on the refutation of atomism, human being is actually a spirit and body is just an instrument. Whereas in the Muʿtazilite school that started off with Abū al-Hudhayl, peaked at al-Qāḍī ʿAbd al-Jabbār and was based on the acceptance of atomism, human being is actually a body and spirit is just a breath incapable of influencing any human actions. These two different attitude toward the conception of human being, have further consequences on the problems of epistemology and ethics. As a matter of fact, al-Naẓẓām and his successors, who accepted the human nature, took up topics like the construction of self, while Abū-Hudhayl and his supporters, who denied the existence of nature or any continuous power, focused on the emergence of action rather than the subject.