Theory of definition in Avicenna

The theory of definition constitutes the essential character of epistemology and ontology, one of the fundamental subjects of the discipline of logic. Thus, definition is one of the two topics at the starting point of knowledge on the epistemic plane. The first of these two subjects is syllogism and the second is definition. This thesis aims to explain how Avicenna (Ibn Sīnā), one of the Islamic logicians, deals with the theory of definition by reflecting his ontological and epistemological perspective within his understanding of philosophy and logic. When definition is evaluated on the logical plane of the logician philosopher, it is analyzed from two perspectives. First, it is the determination and affirmation of existence, and then it is the questioning of what is related to its essence. The thesis consists of an introduction, two chapters and a conclusion. The introduction of the thesis includes the purpose, subject and scope of the research. In the first part of the thesis, the aim is to seek an answer to the question "What is definition?" and to specify the place of definition in Avicenna's logic and to question the elements that will be the basis for definition. In this context, the titles that are important for the logical philosopher, such as concept, essence, proposition, and syllogism, are related to definition in turn. In the second part of the thesis, how the theory of definition is understood in Avicenna and what are the methods for obtaining true knowledge about the existent are discussed. The study titled "The Theory of Definition in Avicenna" is centered on Aristotle and Avicenna, and the problem is discussed and limited in epistemological, ontological and conceptual dimensions by including the views of Islamic logicians on issues related to definition. Following the historical process, the thesis first defines the problem and evaluates the literature. The issue is discussed with the collected data and the findings are concluded.