Cartesian Dualism is the philosophical doctrine proposed by René Descartes, according to which reality consists of two fundamentally different kinds of substances: mind and body. The mind is an immaterial, thinking substance whose essential attribute is thought, while the body is a material substance characterized by extension in space. Descartes argued that the mind is indivisible, conscious, and capable of reasoning, whereas the body is divisible, mechanical, and subject to the laws of physics. This distinction is expressed in his famous statement, "Cogito, ergo sum" ("I think, therefore I am"), which establishes the certainty of the thinking self as the foundation of knowledge. According to Cartesian Dualism, although mind and body are distinct substances, they interact with one another. Descartes suggested that this interaction occurs through the pineal gland, though this explanation has been widely criticized. Cartesian Dualism had a profound influence on modern philosophy by emphasizing the autonomy of reason and the separation of subjective consciousness from the objective material world. It encouraged philosophers to treat knowledge as the product of a detached, rational mind seeking certainty through logical analysis. This view also reinforced sharp distinctions between theory and practice, mind and body, subject and object, and knowledge and action. Pragmatism emerged in the late nineteenth century as a reaction against many assumptions of Cartesian philosophy.