Theoretically, modernism has emphasized the importance of rational thought from the dates when the conceptual foundations were laid. This conception of thought led to a progressive understanding of thought in the Western world, led by reason. The debates that started around the concept of power in the field of social sciences in this period continued to be modern and postmodern. In this context, the modern and postmodern traditions, which evaluated the discussions, interpreted the concepts that started with a focus on power and continued as the source of reality, power and knowledge. Michel Foucault, one of the leading theoreticians of the twentieth century, made a significant impact on the world of thought by proposing a different philosophical form in terms of justice, medicine, psychiatry and sexuality in a wide range from philosophy to psychology, from sociology to etymology. This new philosophical thought formed its own structure by criticizing classical epistemology and ontology. The subject-consciousness-oriented philosophy of knowledge of classical epistemology left its place in Foucault's thought to a discourse and power-centered philosophy of knowledge. Because now there is a multidimensional discourse, order and reality where power is the central concept instead of one truth, one science and one order. The relationship between knowledge and truth and power, power influences between discourses outline this new epistemological / ontological style and Foucault's archaeological and genealogical method. The aim of this study is to reveal how Foucault reshaped the classical tradition of epistemology and ontology on the axis of discourse, order and reality. Furthermore, the relationships between Power, Reality, and knowledge will be judged by Foucault's historical analysis.