It is accepted that the basic element that makes a human beings human is the ‘akl. Human beings also comprehend their responsibilities related to belief, worship and morality with the ‘akl. Thus, the functionality of the ‘akl is directly related to these responsibilities. For this reason, ‘akl is the common subject of disciplines such as philosophy, theology, fiqh (Islamic Law) and sufism. In these disciplines, the relationships between ‘akl-will, ‘akl-faith, ‘akl-nafs and knowledge-sense are some of the subjects that are emphasized, furthermore what the ‘akl can or cannot know, the types of ‘akl, correct ‘akl, the nature and possibility of correct thinking are among the questions asked. However, each of these fields has different approaches to ‘akl. For instance, sufism's approach to ‘akl differs from the others in terms of revealing views and methods that adopt the elimination of evils and vices as obstacles to correct thinking/reasoning and replacing them with goodness and virtues. In this context, Hārith al-Muhāsibī (d. 243/857) argued that correct thinking could be achieved only by training the heart and ‘akl, which he accepts as the source of temperament and actions. Based on the Qur'an, the goal of “being moralized with the morality of Allah”, which is accepted as a principle in Islamic thought, is only possible with correct ‘akl. In other words, being moralized with the morality of Allah or, in Muhāsibī’s words, “obeying Allah's law” (er-ri‘aya li-hukûkillâh/taqwa) is the basic dynamic of correct thinking. With this goal, which is also the name of one of Muhāsibī’s books; It has been regarded as a faculty that needs to be developed in order to fulfill the function of foresight and ingenuity by being matured in terms of consideration, contemplation, remembrance and precaution. Thus, the correct reasoning and perfection of ‘akl can be reached as a result of this process by taking the said target to the center. Although Muhāsibī gives some definitions about the ‘akl and makes evaluations about them, he doesn’t enter into detailed theoretical discussions about the ‘akl. He basically divides the ‘akl into two as innate (ğârîzî) and acquired (muktasab) and focuses on the relationship of the ‘akl with faith, worship and morality, and more on its development in the direction of perfection. In this respect, belief, worship, morality and ‘akl/reasoning are inseparable fields in his thought, and ‘akl becomes perfect to the extent that it takes into account the hereafter. In addition, he especially emphasizes the unity of fear of Allah (havf) regarding the perfection of the ‘akl the strength of certainty (yakîn) in knowledge and belief, prudence in religion and subtle/deep understanding (tafakkuh). In the ‘akl-moral relationship, he puts morality before ‘akl and attributes the perfection of ‘akl by being trained to be purified from disgrace and to be equipped with religious/moral virtues. In other words, Muhāsibī put forward a moral thought centered on faith and tawhid and accepts these as a prerequisite for correct thinking. In this respect, sufi education has basically been accepted as an effort to use the ‘akl correctly and appropriately. It is possible for religious education to benefit from this point of view, which raised important figures in the historical process of sufism. In this way, the aim of this study is to deal with Muhāsibī’s understanding of ‘akl, and to discuss the definition of ‘akl, its scope, the perfection process (education) and the issues that provide it, in the case of Muhāsibī. The research was handled by the method of examining written documents. Accordingly, the data has been revealed with the determinations of Muhāsibī’s different works, especially Mâ(h)iyatu'l-'akl, and a descriptive and interpretive approach has been displayed in their analysis. As a result, this research tries to reveal that Muhāsibī’s understanding of ‘akl, which keeps man's contact with God alive and constantly, can be considered as a meaningful approach in today’s education/religious education. Based on this approach, it can be stated that the religious and moral dimension of education shouldn’t be neglected at the point of using the ‘akl in a true way and that morality should take place more in the education-teaching process. Because, in accordance with the prevailing understanding of the period, it is seen that religion and morality (education) was not considered as a separate phenomenon from general education in Muhāsibī’s thought. In addition, the fact that morality is possible through education with its changeable aspect and that moral values mostly create the upper objectives in education necessitate the regulation of education with a moral attitude and the operation of the process accordingly.