As far as intellectual psychology is concerned, the foundation of psychology as ‘the scientific study of the soul’ in the Ottoman Empire took place between the 1870s and the 1920s, through the surfacing of psychology textbooks with a decreasing number of references to the classical Islamic perspective. Filibeli Ahmed Hilmi contributed to the process of the foundation of psychology through his work İlm-i Ahval el-Ruh [Psychology] (1911/12) by acknowledging the loss of the incontestability of religious sacredness of human nature as exempted creature (müstesna mahluk) from the view of science. In this work psychology was designed to take over the responsibility of establishing the complexity and specialty of human beings. This paper aims to unfold the Ottomans’ responses to the entrance of the medicalization of the human soul and the gradual removal of Islamic perspectives of human nature from the realm of psychology. More specifically it asks the questions (1) to what extent the promotion of man as a controllable, and adjustable entity defined and governed solely by natural laws sparked controversy, (2) to what extent Ahmed Hilmi’s response to physiological reductionism could be understood within one-dimensional paradigms of Islam versus science, materialism versus spiritualism. In the Ottoman context, it is not a coincidence that intellectuals, who engaged in the debate between materialism and spiritualism, made important contributions to the psychological thinking up until the 1920s. Mechanistic explanations of human nature and physiological reductionism constituted the backbones of intellectual discussions as to human nature at the intersection of psychology and biological materialism, which determined Ottoman intellectuals’ answers to the question to which degree science should/could determine human nature. Set against the backdrop of Ottoman modernization, Ahmed Hilmi’s very controlled relationship with science, attributing it great importance while reminding the readers of its limitations, as a cautious participant of scientific circles of his time, exemplifies Ottomans’ efforts to embrace the ‘new,’ - such as medical perspective - in ‘perfect’ doses, while allowing space for certain aspects of the ‘old,’ –such as moral and romantic views of human nature - in the process of Ottoman modernization. This aspect of the debate between materialism and spiritualism helps us contextualize the Ottomans in a global intellectual framework of psychological studies in the early 20th century and have a more nuanced understanding of it.