This study considers the increase and decrease in īmān (belief) in Māturīdism and illustrates the structure and concept of īmān within this school. It is commonly understood that, contrary to the majority of Ash‘arītes and ahl al-ḥadīth (people of ḥadīth), who admit the increase and decrease in īmān, a vast majority of Māturīdītes deny this because, according to their theory, work is not a constituent of īmān, and īmān is composed of only taṣdīq (assent) by the heart, or by another perspective, taṣdīq by the heart and iqrār (confession) by the tongue.
Even among the Māturīdītes, who deny the increase and decrease in īmān, a changeable aspect related to this concept is perceived, but it is believed that the core structure of īmān is unchangeable. The changeable aspect is referred to as nūr (light), ḍiyā’ (brilliance), or thamara (fruit) of īmān. These changeable aspects of īmān are not components of īmān, even though they originate from īmān. However, a group of Māturīdītes, all of whom are scholars from the Ottoman era, believe that īmān is unchangeable only when it refers to mu’man bi-hi (what should be believed), and it accepts the increase and decrease in īmān when it refers to assent.
The author focuses on the following two results of the study. First, those scholars among the Māturīdītes who admit the increase and decrease in īmān are all from the Ottoman era. This perspective could be interpreted as the later Ottoman Māturīdītes' approach to the Ashartes theories on īmān-related issues. Second, the Māturīdītes who admit that there is something changeable, separate these mutable concepts cautiously from the structure of īmān, which are immutable. By doing so, this school succeeds in describing the precise relationship between the concept of īmān and its related concepts.